Study

PHP Tutorial

Credits / Notes taken from:


Table of Contents:

PHP Introduction

What can PHP do?

With PHP you are not limited to output HTML. You can output images, PDF files, and even Flash movies. You can also output any text, such as XHTML and XML.

What’s new in PHP 7? (released December 2015)

Note: PHP 8 was released on November 2020.

PHP Installation using XAMPP

In order to run PHP, we need run an Web Apache Server that processes .php files and sends the output to the browser.
For this, we can install XAMPP distribution (X-Cross Platform, Apache, MariaDB/MySQL, PHP, Perl).

Add C:\xampp\php to Environment Variables (Windows) → path.

If we want the Apache and MySQL to autostart at Windows Startup, we need to open XAMPP Control Panel as Administrator, click on red X to install Apache and MySQL as Window’s Services → click on Config → check on Autostart modules: Apache, MySQL.

https://bitnami.com/stack/xampp#wordpress

All the php files can be accessed from localhost from the C:\xampp\htdocs path. The Apache Server can open all the php files located within than folder. For projects with multiple php files, the path will be C:\xampp\htdocs\myProject.

For the text editor, we can choose:

Useful VSCode extensions for PHP:

Other extensions from blog article on codewall.co.uk

Now, we can start Apache and MySQL server from XAMPP Control Panel, navigate with Windows Explorer to C:\xampp\htdocs\phptutorialsetup, open our CMD Prompt in that location and type code . .
(phptutorialsetup is obtained from this github repo from PHP Tutorial - Traversy Media)

Now, we need to navigate to our http://localhost/phptutorialsetup/ address in Chrome Browser.

Set a new password to MySQL Xampp database

By default, the password for root is an empty string "" (so we don’t have any password).

(Optional) To set a new password for root in MySQL in XAMPP: Configure it with the “XAMPP Shell” (command prompt). Open the shell from the XAMPP control panel and execute this command: mysqladmin.exe -u root password secret this sets the root password to ‘secret’.

After that, we need to edit the C:\xampp\phpMyAdmin\config.inc.php file, and restart both Apache and MySQL servers from XAMPP Control Panel.

Reset Xampp MySQL root password

Now you can access http://localhost/phpmyadmin/.


PHP Syntax

A PHP script starts with <?php and ends with ?>:

<?php
// PHP code goes here
?>

The default file extension for PHP files is “.php”. (unlike Python Django, PHP will not work within .html files !!!)

A PHP file normally contains HTML tags, and some PHP scripting code.

<!DOCTYPE html>
<html>
<body>
<h1>My first PHP page</h1>
<?php
  echo "<h2>Hello World!</h2><br>";
  ECHO "Hello World!<br>";
  EcHo "Hello World!<br>";

  // This is a single-line comment
  # This is also a single-line comment

  /*
  This is a multiple-lines comment block
  that spans over multiple lines
  */

  // You can also use comments to leave out parts of a code line
  $x = 5 /* + 15 */ + 5;
  echo $x;
?>
</body>
</html>

In PHP, keywords (e.g. if, else, while, echo, etc.), classes, functions, and user-defined functions are not case-sensitive. :open_mouth:

However; all variable names are case-sensitive! :ok_hand:

<?php
/*
only the first statement will display
the value of the $color variable!
This is because $color, $COLOR, and $coLOR
are treated as three different variables:
*/
$color = "red";
echo "My car is " . $color . "<br>";
echo "My house is " . $COLOR . "<br>";
echo "My boat is " . $coLOR . "<br>";
?>

PHP Variables

In PHP, a variable starts with the $ sign, followed by the name of the variable. In PHP (as it’s dynamically written language) variables don’t have types.

$txt = "Hello world!";
$x = 5;
$y = 10.5;
echo $x + $y;
echo "<hr/>";
$name = "Radu";
echo "$txt my name is $name";

Rules for PHP variables:

In PHP 7, type declarations were added. This gives an option to specify the data type expected when declaring a function, and by enabling the strict requirement, it will throw a “Fatal Error” on a type mismatch.

PHP Variables Scope

https://www.w3schools.com/php/php_variables_scope.asp

PHP has three different variable scopes:

A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function:

<?php
$x = 5; // global scope

function myTest() {
  // using x inside this function will generate an error
  echo "<p>Variable x inside function is: $x</p>";
}
myTest();

echo "<p>Variable x outside function is: $x</p>";
?>

A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function:

<?php
function myTest() {
  $x = 5; // local scope
  echo "<p>Variable x inside function is: $x</p>";
}
myTest();

// using x outside the function will generate an error
echo "<p>Variable x outside function is: $x</p>";
?>

PHP The global Keyword

The global keyword is used to access a global variable from within a function.

<?php
$x = 5;
$y = 10;
function myTest() {
  global $x, $y;
  $y = $x + $y;
}
myTest();
echo $y; // outputs 15

/* Note, you can't declare global variables like this:
global $x = 5; // it will give a Parse error...
global $y = 10;
function myTest() {
  $y = $x + $y;
}
myTest();
*/

/* Note, if you don't declare the varibles as global outside function
$x = 5;
$y = 10;
global $x, $y;
function myTest() {
  $y = $x + $y; // it will give Undefined variable: x, y
}
myTest();
*/
?>

PHP also stores all global variables in an array called $GLOBALS[*index*]. The index holds the name of the variable. This array is also accessible from within functions and can be used to update global variables directly.

<?php
$x = 5;
$y = 10;

function myTest() {
  $GLOBALS['y'] = $GLOBALS['x'] + $GLOBALS['y'];
}

myTest();
echo $y; // outputs 15
?>


PHP The static keyword

Normally, when a function is completed/executed, all of its variables are deleted. However, sometimes we want a local variable NOT to be deleted. We need it for a further job. To do this, use the static keyword when you first declare the variable:

<?php
function myTest2() {
  static $x = 0;
  echo $x."<br>";
  $x++;
}

myTest2(); // 1
myTest2(); // 2
myTest2(); // 3

/* each time the function is called,
that variable will still have the information
it contained from the last time the function was called. */
?>

PHP Debug / Print to JS Console function

(Thu, February 04, 2021) Okay, maybe it’s just me… but I’ve noted that, I don’t have any console in PHP …

However, instead of using echo, var_dump(), get_type(), print_r() functions and render directly in HTML code… I came across this function

function console_log( $data ){
  echo '<script>';
  echo 'console.log('. json_encode( $data ) .')';
  echo '</script>';
}

// Usage:
$myvar = array("Banana", "Apple", "Orange");
console_log( $myvar );

Now we can use console_log(); to print to Browser’s console, just like in JavaScript (console.log();)… except, we are actually using JavaScript ofc. :laughing:

PHP Data types and operators

PHP Data types, var_dump(), check functions

The PHP var_dump() function returns the data type and value (basically prints out all the information of a variable).

The print_r() prints human-readable information about a variable

The PHP function gettype($name) function returns only the data type.

PHP supports the following data types:

$txt = "Hello world!"; // 12 characters
var_dump($txt); // string(12)
echo gettype($txt); // string

// We can concatenate strings using . (dot)
echo $txt . " How are you?" . "<br/>"; // Hello world! How are you?
// or
echo "$txt How are you?<br/>"; // Hello world! How are you?

$x = 52;
var_dump($x); // int(52)
echo gettype($x); // integer

$x = 10.365;
var_dump($x); // float(10.365)
echo gettype($x); // double

$x = true;
$y = false;
var_dump(x); // bool(true)
echo gettype($x); // boolean
echo $x; // 1
echo $y; //

// Whenever booleans are converted into strings:
// true is converted into "1"
// false is converted into empty string "" (which will not show anything in html)

$cars = array("Volvo","BMW","Toyota");
var_dump($cars);
// array(3) { [0]=> string(5) "Volvo" [1]=> string(3) "BMW" [2]=> string(6) "Toyota" }

$nested_array = array(array("red", "green"), "blue");
// array(2) { [0]=> array(2) { [0]=> string(3) "red" [1]=> string(5) "green" } [1]=> string(4) "blue" }

// If a variable is created without a value, it is automatically assigned a value of NULL.
// Variables can also be emptied by setting the value to NULL:
$x = "Hello world!";
$x = null;
var_dump($x); // NULL
echo gettype($x); // NULL
echo $x; //

// null is converted into an empty string "" as well

/* with __construct() function,
PHP will automatically call this function when you create an object from a class.
*/
class Car {
  public $color;
  public $model;
  public function __construct($color, $model) {
    $this->color = $color;
    $this->model = $model;
  }
  public function message() {
    return "My car is a " . $this->color . " " . $this->model . "!";
    // or
    // return "My car is a $this->color $this->model!";
  }
}

$myCar = new Car("black", "Volvo");
echo $myCar -> message(); // My car is a black Volvo!
echo "<br>";
$myCar = new Car("red", "Toyota");
echo $myCar -> message(); // My car is a red Toyota!

var_dump($myCar); // object(Car)#2 (2) { ["color"]=> string(3) "red" ["model"]=> string(6) "Toyota" }
echo gettype($x); // object

The special resource type is not an actual data type. It is the storing of a reference to functions and resources external to PHP. A common example of using the resource data type is a database call.


Variable checking functions

var_dump("Hello"); // string(5) "Hello"
echo gettype("Hello"); // string

is_string($name); // false
is_int($age); // true
is_double($height); // true
is_bool($isMale); // true

/* However these functions will not print anything in HTML
... and you cannot use echo is_double($var)... because if
it's false, it will not print anything in HTML...
So, the safest way to check is with: */

var_dump(is_string($name)); // bool(false)
var_dump(is_int($age)); // bool(true)
var_dump(is_double($height)); // bool(true)
var_dump(is_bool($isMale)); // bool(true)


Check if variable is declared/defined

$name = "Alex";
isset($name); // true
isset($address); // false

PHP Constants

To declare CONSTANT variables (const) in PHP, we use define (just like in C/C++):

define(name, value, case_insensitive);

Example:

define('PI', 3.14);

// to use/print a constant, we don't use $ anymore
echo PI; // 3.1415

// predefined constants in PHP
echo PHP_INT_MAX.'<br>'; // 9223372036854775807
echo PHP_FLOAT_MAX.'<br>'; // 1.7976931348623E+308

Example:

<?php
define("GREETING", "Welcome aboard, Captain!", true);
echo greeting; // Welcome aboard, Captain!
?>


PHP Constant Arrays

In PHP7, you can create an Array constant using the define() function.

<?php
define("cars", [
  "Alfa Romeo",
  "BMW",
  "Toyota"
]);
echo cars[0]; // Alfa Romeo
?>


NOTE: Constants are automatically global and can be used across the entire script.


PHP Operators

https://www.w3schools.com/php/php_operators.asp

PHP Arithmetic Operators

Operator Name Example Result
+ Addition $x + $y Sum of $x and $y
- Subtraction $x - $y Difference of $x and $y
* Multiplication $x * $y Product of $x and $y
/ Division $x / $y Quotient of $x and $y
% Modulus $x % $y Remainder of $x divided by $y
** Exponentiation $x ** $y Result of raising $x to the $y’th power

PHP Comparison Operators

Operator Name Example Result
== Equal $x == $y Returns true if $x is equal to $y
=== Identical $x === $y Returns true if $x is equal to $y,
and they are of the same type
!= Not equal $x != $y Returns true if $x is not equal to $y
<> Not equal $x <> $y Returns true if $x is not equal to $y
!== Not identical $x !== $y Returns true if $x is not equal to $y,
or they are not of the same type
> Greater than $x > $y Returns true if $x is greater than $y
< Less than $x < $y Returns true if $x is less than $y
>= Greater than or equal to $x >= $y Returns true if $x is greater than or equal to $y
<= Less than or equal to $x <= $y Returns true if $x is less than or equal to $y
<=> Spaceship $x <=> $y Returns an integer less than, equal to,
or greater than zero, depending on if $x is less
than, equal to, or greater than $y.
Introduced in PHP 7.

PHP Logical Operators

Operator Name Example Result
and And $x and $y True if both $x and $y are true
or Or $x or $y True if either $x or $y is true
xor Xor $x xor $y True if either $x or $y is true,
but not both
&& And $x && $y True if both $x and $y are true
\|\| Or $x \|\| $y True if either $x or $y is true
! Not !$x True if $x is not true

PHP Increment / Decrement Operators

Operator Name Description
++$x Pre-increment Increments $x by one, then returns $x
$x++ Post-increment Returns $x, then increments $x by one
--$x Pre-decrement Decrements $x by one, then returns $x
$x-- Post-decrement Returns $x, then decrements $x by one

PHP String Operators

Operator Name Example Result
. Concatenation $txt1 . $txt2 Concatenation of $txt1 and $txt2
.= Concatenation assignment $txt1 .= $txt2 Appends $txt2 to $txt1

PHP Array Operators

Operator Name Example Result
+ Union $x + $y Union of $x and $y
== Equality $x == $y Returns true if $x and $y
have the same key/value pairs
=== Identity $x === $y Returns true if $x and $y
have the same key/value pairs
in the same order and of the same types
!= Inequality $x != $y Returns true if $x is not equal to $y
<> Inequality $x <> $y Returns true if $x is not equal to $y
!== Non-identity $x !== $y Returns true if $x is not identical to $y

PHP Conditional Assignment Operators

Operator Name Example Result
?: Ternary $x = expr1 ? expr2 : expr3 Returns the value of $x. The value of $x is expr2 if expr1 = TRUE. The value of $x is expr3 if expr1 = FALSE
?? Null coalescing $x = expr1 ?? expr2 Returns the value of $x. The value of $x is expr1 if expr1 exists, and is not NULL. If expr1 does not exist, or is NULL, the value of $x is expr2. Introduced in PHP 7


PHP Numbers

https://www.w3schools.com/php/php_numbers.asp

echo 0.2 + 0.1; // 0.3

/* Note that the result with echo is trimmed and we don't see a floating point number */
// But
var_dump(.1 + .2); // float(0.30000000000000004441)
var_dump(.2 + .1 === 0.3); // bool(false)

# Python
print(0.2 + 0.3) # 0.30000000000000004
// JavaScript (Node.js)
console.log(0.2 + 0.3); // 0.30000000000000004

PHP Integers and floats/doubles

<?php
$x = 10.365;
var_dump(is_float($x)); // bool(true)

$x = 10
var_dump(is_int($x)); // bool(true)
?>

PHP Infinity

A numeric value that is larger than PHP_FLOAT_MAX is considered infinite.

PHP has the following functions to check if a numeric value is finite or infinite:

echo PHP_FLOAT_MAX.'<br>'; // 1.7976931348623E+308

$x = 1.9e411;
var_dump($x); // float(INF)

var_dump(is_infinite($x)); // bool(true)
var_dump(is_finite($x)); // bool(false)

var_dump(is_finite(43)); // true


PHP NaN (Not a Number)

NaN is used for impossible mathematical operations. PHP has the following functions to check if a value is not a number:

// Invalid calculation will return a NaN value
$x = acos(8);
var_dump($x); // float(NAN)


PHP Numerical Strings

The PHP is_numeric() function can be used to find whether a variable is numeric. The function returns true if the variable is a number or a numeric string, false otherwise.

$x = 5985;
var_dump(is_numeric($x)); // bool(true)

$x = "5985";
var_dump(is_numeric($x)); // bool(true)

$x = "59.85" + 100;
var_dump(is_numeric($x)); // bool(true)

$x = "Hello";
var_dump(is_numeric($x)); // bool(false)

PHP Casting Strings and Floats to Integers

// Cast float to int
$x = 23465.768;
$int_cast = (int)$x;
echo $int_cast; // 23465

echo "<br>";

// Cast string to int
$x = "23465.768";
$int_cast = (int)$x;
echo $int_cast; // 23465

// Cast string to float
$float_cast = (float)$x;

Other ways of casting using functions:

$strNumber = '12.23';
$number = intval($strNumber);
var_dump($number); // int(12)

echo "<br/>";

var_dump(floatval("12.23")); // float(12.23)

PHP Number formatting

number_format($number, $decimals = 0, $dec_point = '.', $thousands_sep = ',')

$number = 123456789.12345;
echo number_format($number, 2, '.', " "); // 123 456 789.12
echo number_format($number, 2, '.', ","); // 123,456,789.12


PHP Math

https://www.w3schools.com/php/php_math.asp

PHP pi() function

echo(pi()); // returns 3.1415926535898

PHP min() and max() Functions

echo(min(0, 150, 30, 20, -8, -200));  // returns -200
echo(max(0, 150, 30, 20, -8, -200));  // returns 150

PHP abs() (absolute value) Function

echo(abs(-6.7));  // returns 6.7

PHP sqrt() Function

echo(sqrt(64));  // returns 8

PHP round() Function

echo(round(0.60));  // returns 1
echo(round(0.49));  // returns 0

PHP floor and ceil

echo(floor(0.60)); // 0
echo(ceil(0.49)); // 1

Random Numbers

echo(rand()); // 1381167960
echo(rand(10, 100)); // 97

All PHP Math Functions

Function Description
abs() Returns the absolute (positive) value of a number
acos() Returns the arc cosine of a number
acosh() Returns the inverse hyperbolic cosine of a number
asin() Returns the arc sine of a number
asinh() Returns the inverse hyperbolic sine of a number
atan() Returns the arc tangent of a number in radians
atan2() Returns the arc tangent of two variables x and y
atanh() Returns the inverse hyperbolic tangent of a number
base_convert() Converts a number from one number base to another
bindec() Converts a binary number to a decimal number
ceil() Rounds a number up to the nearest integer
cos() Returns the cosine of a number
cosh() Returns the hyperbolic cosine of a number
decbin() Converts a decimal number to a binary number
dechex() Converts a decimal number to a hexadecimal number
decoct() Converts a decimal number to an octal number
deg2rad() Converts a degree value to a radian value
exp() Calculates the exponent of e
expm1() Returns exp(x) - 1
floor() Rounds a number down to the nearest integer
fmod() Returns the remainder of x/y
getrandmax() Returns the largest possible value returned by rand()
hexdec() Converts a hexadecimal number to a decimal number
hypot() Calculates the hypotenuse of a right-angle triangle
intdiv() Performs integer division
is_finite() Checks whether a value is finite or not
is_infinite() Checks whether a value is infinite or not
is_nan() Checks whether a value is ‘not-a-number’
lcg_value() Returns a pseudo random number in a range between 0 and 1
log() Returns the natural logarithm of a number
log10() Returns the base-10 logarithm of a number
log1p() Returns log(1+number)
max() Returns the highest value in an array, or the highest value of several specified values
min() Returns the lowest value in an array, or the lowest value of several specified values
mt_getrandmax() Returns the largest possible value returned by mt_rand()
mt_rand() Generates a random integer using Mersenne Twister algorithm
mt_srand() Seeds the Mersenne Twister random number generator
octdec() Converts an octal number to a decimal number
pi() Returns the value of PI
pow() Returns x raised to the power of y
rad2deg() Converts a radian value to a degree value
rand() Generates a random integer
round() Rounds a floating-point number
sin() Returns the sine of a number
sinh() Returns the hyperbolic sine of a number
sqrt() Returns the square root of a number
srand() Seeds the random number generator
tan() Returns the tangent of a number
tanh() Returns the hyperbolic tangent of a number

https://www.php.net/manual/en/ref.math.php


PHP Dates

Print the number of seconds since 01.01.1970

echo time(); // 1631120754

Print the current date using formatting:

echo date('Y-m-d H:i:s'); // 2021-09-08 19:00:23

Print the yesterday’s date using a timestamp parameter, where we specify the time minus the day in seconds (there are 60 * 60 * 24 seconds in a day)

// Print yesterday's date
echo date('Y-m-d H:i:s', time() - 60 * 60 * 24); // 2021-09-07 19:02:56

// Print tomorrow's date
echo date('Y-m-d H:i:s', time() + 60 * 60 * 24); // 2021-09-07 19:02:56

More examples using date formats

echo date('F j Y, H:i:s'); // September 8 2021, 19:04:34

Another example of getting the current date in PHP in a specific format:

function getTodayDateFormatted() {
  return date("l, F d, Y");
}
echo getTodayDateFormatted(); // Saturday, September 04, 2021

Parse dates from HTML forms (will return an associative array):

$parseDate = date_parse('2021-08-12 09:00:00');

echo "<pre>";
var_dump($parseDate);
echo "</pre>";

/* returns
array(12) {
  ["year"]=>
  int(2021)
  ["month"]=>
  int(8)
  ["day"]=>
  int(12)
  ["hour"]=>
  int(9)
  ["minute"]=>
  int(0)
  ["second"]=>
  int(0)
  ["fraction"]=>
  float(0)
  ["warning_count"]=>
  int(0)
  ["warnings"]=>
  array(0) {
  }
  ["error_count"]=>
  int(0)
  ["errors"]=>
  array(0) {
  }
  ["is_localtime"]=>
  bool(false)
}
*/


Parse a date from in a different format (form a different source, other than HTML form) using date_parse_from_format. Here we need to specify the format of the date received in a way that PHP will print it using it’s date() formatting options:

$dateString = 'February 12 2021 12:54:34';
$parseDate = date_parse_from_format('F j Y H:i:s', $dateString);

echo "<pre>";
var_dump($parseDate);
echo "</pre>";

/* returns
array(12) {
  ["year"]=>
  int(2021)
  ["month"]=>
  int(2)
  ["day"]=>
  int(12)
  ["hour"]=>
  int(12)
  ["minute"]=>
  int(54)
  ["second"]=>
  int(34)
  ["fraction"]=>
  float(0)
  ["warning_count"]=>
  int(0)
  ["warnings"]=>
  array(0) {
  }
  ["error_count"]=>
  int(0)
  ["errors"]=>
  array(0) {
  }
  ["is_localtime"]=>
  bool(false)
}
*/

Note that it will also work using just date_parse()

$dateString = 'February 12 2021 12:54:34';
$parseDate = date_parse($dateString);


PHP String methods

(Friday, February 05, 2021)

Strings concatenation (Note that the use of single or double quotes matters)

$name = "Alex";
echo 'Hi I am '.$name.'!<br/>'; // Hi I am Alex!
echo 'Hi I am $name!<br/>'; // Hi I am $name!
echo "Hi I am $name!<br/>"; // Hi I am Alex!


strlen, trim, strpos, substr, str_replace

strlen() - Return the Length of a String

echo strlen("Hello world!"); // outputs 12


trim() - Removes whitespace from both sides of a string
For right or left side, use rtrim() / ltrim()

echo trim("   Hi, World!   "); // Hi, World!


str_word_count() - Count Words in a String

echo str_word_count("Hello world!"); // outputs 2


strrev() - Reverse a String

echo strrev("Hello world!"); // !dlrow olleH


strpos() - Search For a Text Within a String (case sensitive), returns the first characters position of the first match, if no match is found, returns false

echo strpos("Hello world!", "world"); // 6

stripos() - Search For a Text Within a String (ignore case sensitive)

echo strpos("Hello World!", "world"); // 6


substr() - Returns part of a string (substring)

echo substr("Hello World", 4);  // o World
echo substr("Hello World", -4); // orld

echo substr("Hello World", 4, 3); // O W (takes only 3 characters from pos 4)


str_replace() - Replace Text (all occurrences) within a String
str_ireplace() (ignore case sensitive)

echo str_replace("world", "Captain", "Hello world!"); // Hello Captain!
echo str_ireplace("hello", "Captain", "Hello? hello!"); // Captain? Captain!


strtolower() and strtoupper() converts string to Lower Case / Upper Case

echo strtolower("Hello World"); // hello world
echo strtoupper("Hello World"); // HELLO WORLD

ucfirst() and lcfirst() converts to Upper Case / Lower Case only the first character

echo ucfirst("hello world"); // Hello world
echo lcfirst("HELLO WORLD"); // hELLO WORLD

ucwords() Upper Case all words in string

echo ucwords("hello world"); // Hello World


nl2br() - newline to break line

$longText = "
  Hi,
  I'm Alex,
  I like back-end.
";

echo $longText.'<br>'; // Hi, I'm Alex, I like back-end.
echo nl2br($longText).'<br>';
// Hi,
// I'm Alex,
// I like back-end.


String indexes, PHP Strings are mutable

We can access string character’s with [ ]:

echo "Hello"[0]; // H
echo "Hello"[1]; // e
echo "Hello"[-1]; // o

Unlike JavaScript and Python… Strings in PHP are mutable (content can be changed without creating a new object).

$myStr = "hello";
$myStr[0] = "j";
$myStr[-1] = 'y';
echo $myStr; // jelly


String Explode, Array Implode

explode() Breaks a string into an array (in JavaScript/Python we have str.split())

explode ( string `$separator` , string `$string` , int `$limit` = `PHP_INT_MAX`) : array

$pizza  = "piece1 piece2 piece3";
$pieces = explode(" ", $pizza);
echo $pieces[0]; // piece1
echo $pieces[1]; // piece2

implode() Returns a string from the elements of an array (join() does the same, is an alias of implode())

$arr = array('Test1', 'Test2', 'Test3');
$str = join(",", $arr);
echo $str; // Test1,Test2,Test3.
![PHP Explode meme](/Study/PHP/PhpTutorial/03.jpg)


All PHP String Methods

Function Description
addcslashes() Returns a string with backslashes in front of the specified characters
addslashes() Returns a string with backslashes in front of predefined characters
bin2hex() Converts a string of ASCII characters to hexadecimal values
chop() Removes whitespace or other characters from the right end of a string
chr() Returns a character from a specified ASCII value
chunk_split() Splits a string into a series of smaller parts
convert_cyr_string() Converts a string from one Cyrillic character-set to another
convert_uudecode() Decodes a uuencoded string
convert_uuencode() Encodes a string using the uuencode algorithm
count_chars() Returns information about characters used in a string
crc32() Calculates a 32-bit CRC for a string
crypt() One-way string hashing
echo() Outputs one or more strings
explode() Breaks a string into an array
fprintf() Writes a formatted string to a specified output stream
get_html_translation_table() Returns the translation table used by htmlspecialchars() and htmlentities()
hebrev() Converts Hebrew text to visual text
hebrevc() Converts Hebrew text to visual text and new lines (\n) into
hex2bin() Converts a string of hexadecimal values to ASCII characters
html_entity_decode() Converts HTML entities to characters
htmlentities() Converts characters to HTML entities
htmlspecialchars_decode() Converts some predefined HTML entities to characters
htmlspecialchars() Converts some predefined characters to HTML entities
implode() Returns a string from the elements of an array
join() Alias of implode()
lcfirst() Converts the first character of a string to lowercase
levenshtein() Returns the Levenshtein distance between two strings
localeconv() Returns locale numeric and monetary formatting information
ltrim() Removes whitespace or other characters from the left side of a string
md5() Calculates the MD5 hash of a string
md5_file() Calculates the MD5 hash of a file
metaphone() Calculates the metaphone key of a string
money_format() Returns a string formatted as a currency string
nl_langinfo() Returns specific local information
nl2br() Inserts HTML line breaks in front of each newline in a string
number_format() Formats a number with grouped thousands
ord() Returns the ASCII value of the first character of a string
parse_str() Parses a query string into variables
print() Outputs one or more strings
printf() Outputs a formatted string
quoted_printable_decode() Converts a quoted-printable string to an 8-bit string
quoted_printable_encode() Converts an 8-bit string to a quoted printable string
quotemeta() Quotes meta characters
rtrim() Removes whitespace or other characters from the right side of a string
setlocale() Sets locale information
sha1() Calculates the SHA-1 hash of a string
sha1_file() Calculates the SHA-1 hash of a file
similar_text() Calculates the similarity between two strings
soundex() Calculates the soundex key of a string
sprintf() Writes a formatted string to a variable
sscanf() Parses input from a string according to a format
str_getcsv() Parses a CSV string into an array
str_ireplace() Replaces some characters in a string (case-insensitive)
str_pad() Pads a string to a new length
str_repeat() Repeats a string a specified number of times
str_replace() Replaces some characters in a string (case-sensitive)
str_rot13() Performs the ROT13 encoding on a string
str_shuffle() Randomly shuffles all characters in a string
str_split() Splits a string into an array
str_word_count() Count the number of words in a string
strcasecmp() Compares two strings (case-insensitive)
strchr() Finds the first occurrence of a string inside another string (alias of strstr())
strcmp() Compares two strings (case-sensitive)
strcoll() Compares two strings (locale based string comparison)
strcspn() Returns the number of characters found in a string before any part of some specified characters are found
strip_tags() Strips HTML and PHP tags from a string
stripcslashes() Unquotes a string quoted with addcslashes()
stripslashes() Unquotes a string quoted with addslashes()
stripos() Returns the position of the first occurrence of a string inside another string (case-insensitive)
stristr() Finds the first occurrence of a string inside another string (case-insensitive)
strlen() Returns the length of a string
strnatcasecmp() Compares two strings using a “natural order” algorithm (case-insensitive)
strnatcmp() Compares two strings using a “natural order” algorithm (case-sensitive)
strncasecmp() String comparison of the first n characters (case-insensitive)
strncmp() String comparison of the first n characters (case-sensitive)
strpbrk() Searches a string for any of a set of characters
strpos() Returns the position of the first occurrence of a string inside another string (case-sensitive)
strrchr() Finds the last occurrence of a string inside another string
strrev() Reverses a string
strripos() Finds the position of the last occurrence of a string inside another string (case-insensitive)
strrpos() Finds the position of the last occurrence of a string inside another string (case-sensitive)
strspn() Returns the number of characters found in a string that contains only characters from a specified charlist
strstr() Finds the first occurrence of a string inside another string (case-sensitive)
strtok() Splits a string into smaller strings
strtolower() Converts a string to lowercase letters
strtoupper() Converts a string to uppercase letters
strtr() Translates certain characters in a string
substr() Returns a part of a string
substr_compare() Compares two strings from a specified start position (binary safe and optionally case-sensitive)
**substr_count()** Counts the number of times a substring occurs in a string
substr_replace() Replaces a part of a string with another string
trim() Removes whitespace or other characters from both sides of a string
ucfirst() Converts the first character of a string to uppercase
ucwords() Converts the first character of each word in a string to uppercase
vfprintf() Writes a formatted string to a specified output stream
vprintf() Outputs a formatted string
vsprintf() Writes a formatted string to a variable
wordwrap() Wraps a string to a given number of characters


PHP Arrays

There are two ways to create indexed arrays:

The index can be assigned automatically (index always starts at 0), like this:

$cars = array("Volvo", "BMW", "Toyota");

or like this:

$cars = ["Volvo", "BMW", "Toyota"];
var_dump($cars);
// array(3) { [0]=> string(5) "Volvo" [1]=> string(3) "BMW" [2]=> string(6) "Toyota" }

echo $cars[0]; // Volvo
echo $cars[1]; // BMW
echo $cars[2]; // Toyota

or we can set elements by index manually (without declaring $cars first):

$cars[0] = "Volvo";
$cars[1] = "BMW";
$cars[2] = "Toyota";


Print all the contents of an array while nicely formated:

$fruits = ["Banana", "Apple", "Orange"];
echo '<pre>';
var_dump($fruits);
echo '</pre>';

array(3) {
  [0]=>
  string(5) "Banana"
  [1]=>
  string(5) "Apple"
  [2]=>
  string(6) "Orange"
}


Loop through an Indexed Array using a for loop

$fruits = ["Banana", "Apple", "Orange"];

for($i = 0; $i < count($fruits); $i++) {
  echo $fruits[$i].'<br>';
}
/*
Banana
Apple
Orange */

Array methods

(Saturday, February 06, 2021)

count, push, pop, unshift, shift

Get the length of array with count()

$fruits = ["Banana", "Apple", "Orange"];
echo count($fruits); // 3

sizeof() it’s an alias of count() (it’s the same function)

echo sizeof($fruits); // 3


Check if array has an element at index

isset($fruits[2]); // true
var_dump(isset($fruits[2])); // bool(true)


Append element at the end of Array

$fruits[] = 'Kiwi';
var_dump($fruits);
// array(4) { [0]=> string(5) "Banna" [1]=> string(5) "Apple" [2]=> string(6) "Orange" [3]=> string(4) "Kiwi" }

// Note that
$fruits[] = ['Kiwi', 'Mango'];
// will append an array to the end of the array.

array(4) {
  [0]=>
  string(5) "Banna"
  [1]=>
  string(5) "Apple"
  [2]=>
  string(6) "Orange"
  [3]=>
  array(2) {
    [0]=>
    string(4) "Kiwi"
    [1]=>
    string(5) "Mango"
  }
}

^^ So with this, we can create an array just by appending using $array[] = "element"

// example: Array with names
$a[] = "Anna";
$a[] = "Brittany";
$a[] = "Cindy";
$a[] = "Diana";
$a[] = "Eva";
$a[] = "Fiona";


We can also append multiple elements to array using array_push()

$fruits = ["Banana", "Apple", "Orange"];
array_push($fruits, "Kiwi", "Raspberry");

print_r($fruits);
// Array ( [0] => Banana [1] => Apple [2] => Orange [3] => Kiwi [4] => Raspberry )


Remove (pop) element from the end of Array (and also return it)

$fruits = ["Banana", "Apple", "Orange"];
echo array_pop($fruits); // Orange
print_r($fruits); // Array ( [0] => Banana [1] => Apple )


Add element at the beginning of the array with array_unshift()

$fruits = ["Banana", "Apple", "Orange"];
array_unshift($fruits, 'Pineapple');
print_r($fruits); // Array ( [0] => Pineapple [1] => Banana [2] => Apple [3] => Orange )


Remove element from the beginning of the array with array_shift()

$fruits = ["Banana", "Apple", "Orange"];
array_shift($fruits);
// Array ( [0] => Apple [1] => Orange )


String Explode, Array Implode

explode ( string `$separator` , string `$string` , int `$limit` = `PHP_INT_MAX` ) : array

$fruits = explode(",", "Banana,Apple,Orange");
print_r($fruits); // Array ( [0] => Banana [1] => Apple [2] => Orange )

implode ( string `$separator` , array `$array` ) : string

$fruits = ["Banana", "Apple", "Orange"];
echo implode(", ", $fruits); // Banana, Apple, Orange


Check if element in array, get index of element

Check if element exists in Array with in_array()

$fruits = ["Banana", "Apple", "Orange"];
var_dump(in_array('Apple', $fruits)); // bool(true)
var_dump(in_array('Lemon', $fruits)); // bool(false)

Return element’s index in Array (if exists) with array_search()

$fruits = ["Banana", "Apple", "Orange"];
var_dump(array_search('Apple', $fruits)); // int(1)
var_dump(array_search('Lemon', $fruits)); // bool(false)


Merge arrays, chunk arrays

Return merged array from two or more arrays with array_merge()

$fruits = ["Banana", "Apple", "Orange"];
$veggies = ["Potato", "Cucumber"];
print_r(array_merge($fruits, $veggies));
// Array ( [0] => Banana [1] => Apple [2] => Orange [3] => Potato [4] => Cucumber )

From PHP 7.4 and above, we can use the Spread operator to merge arrays:

print_r( [...$fruits, ...$veggies] );
// Array ( [0] => Banana [1] => Apple [2] => Orange [3] => Potato [4] => Cucumber )


The array_chunk() function splits an array into chunks of new arrays.

$cars = array("Volvo","BMW","Toyota","Honda","Mercedes");
echo "<pre>";
print_r(array_chunk($cars, 2));
echo "</pre>";

Array
(
    [0] => Array
        (
            [0] => Volvo
            [1] => BMW
        )
    [1] => Array
        (
            [0] => Toyota
            [1] => Honda
        )
    [2] => Array
        (
            [0] => Mercedes
        )
)


Sort Arrays

$fruits = ["Banana", "Apple", "Orange"];
sort($fruits);
print_r($fruits); // Array ( [0] => Apple [1] => Banana [2] => Orange )

$numbers = array(4,6,2,22,11);
sort($numbers);
echo(join(', ', $numbers)); // 2, 4, 6, 11, 22

(sort($arr) mutates the array and returns true on success, false on failure)

PHP Associative Arrays (Dictionaries/JS Objects)

Associative arrays are key-value pairs.

They are the equivalent of dictionaries in Python or objects in JavaScript. All in all, associative arrays are like JSON in PHP’s coat (the same applies for objects in JavaScript, this data format is JSON - read more here).

Example:

$ages = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
// Array ( [Peter] => 35 [Ben] => 37 [Joe] => 43 )

Another example:

$person = [
  'name' => 'Brad',
  'surname' => 'Traversy',
  'age' => 30,
  'hobbies' => ['Tennis', 'Video Games']
];
echo "<pre>";
print_r($person);
echo "</pre>";

Output:

Array
(
    [name] => Brad
    [surname] => Traversy
    [age] => 30
    [hobbies] => Array
        (
            [0] => Tennis
            [1] => Video Games
        )
)


Let’s compare the same “associative array” to a JavaScript object:

// JavaScript
let person = {
  name: "Brad",
  surname: "Traversy",
  age: 30,
  hobbies: ["Tennis", "Video Games"],
};
console.log(person);

Output:

{name: "Brad", surname: "Traversy", age: 30, hobbies: Array(2)}
  age: 30
  hobbies: (2) ["Tennis", "Video Games"]
  name: "Brad"
  surname: "Traversy"


Associative Array simple methods

Loop Through an Associative Array

$person = [
  'name' => 'Brad',
  'surname' => 'Traversy',
  'age' => 30,
  'hobbies' => ['Tennis', 'Video Games']
];

foreach($person as $key => $value) {
  echo($key.": ");
  print_r($value);
  echo("<br/>");
}

name: Brad
surname: Traversy
age: 30
hobbies: Array ( [0] => Tennis [1] => Video Games )


Get/Set/Check element in array by key

$person = [
  'name' => 'Brad',
  'surname' => 'Traversy',
  'age' => 30,
  'hobbies' => ['Tennis', 'Video Games']
];

echo $person['name']; // Brad
$person['age'] = 34;

if (!isset($person['address'])) {
  // if $person addres does not exist, add and set the 'address' key to 'unknown' value
  $person['address'] = 'unknown';
}

PHP Associative Arrays


However, from PHP 7.4, we can check and set a value to a non-existing key with double question marks ??:

$person['address'] ??= 'unknown';

// same as
$person['address'] = $person['address'] ?? 'unknown';

// same as
if (!isset($person['address'])) {
  $person['address'] = 'unknown';
}


If we want to print out the keys of an associative array, we use array_keys($arr)

echo '<pre>';
var_dump(array_keys($person));
echo '</pre>';

PHP Associative Arrays

And to print our an associative array values, we use array_values()

echo '<pre>';
var_dump(array_values($person));
echo '</pre>';


Sort Associative array

We can sort associative arrays by keys using ksort($assoc_array):

$person = [
  'name' => 'Brad',
  'surname' => 'Traversy',
  'age' => 30,
  'hobbies' => ['Tennis', 'Video Games']
];
ksort($person);

echo "<pre>";
print_r($person);
echo "</pre>";

Or we can sort associative arrays by values using asort($assoc_array)

$person = [
  'name' => 'Brad',
  'surname' => 'Traversy',
  'age' => 30,
  'hobbies' => ['Tennis', 'Video Games']
];
asort($person);

PHP Associative Arrays


Sort a associative multidimensional array

If we want to sort by the values of “price” key (source here)

$inventory = array(
   array("type"=>"pork", "price"=>5.43),
   array("type"=>"fruit", "price"=>3.50),
   array("type"=>"milk", "price"=>2.90),
);

/* For PHP < 5.5 */
$price = array();
foreach ($inventory as $key => $row) {
    $price[$key] = $row['price'];
}
array_multisort($price, SORT_DESC, $inventory);

/* For PHP > 5.5 */
$price = array_column($inventory, 'price');
array_multisort($price, SORT_DESC, $inventory);

/* For PHP > 7.0 */
// Ascending
usort($inventory, function ($item1, $item2) {
    return $item1['price'] <=> $item2['price'];
});

// Descending
usort($inventory, function ($item1, $item2) {
    return $item2['price'] <=> $item1['price'];
});

<=>, the spaceship comparison operator, returns 0 if both operands are equal, 1 if the left is greater, and -1 if the right is greater


Two dimensional Array like JS Objects

<?php
$todos = [
  ['title' => 'Todo title 1', 'completed' => true],
  ['title' => 'Todo title 2', 'completed' => false],
  ['title' => 'Todo title 3', 'completed' => true]
];

PHP Associative Arrays

(This is how the data might look like when we are using REST API - same as with JavaScript Objects / JSON)


PHP conditionals and loops

PHP conditionals

if.. elseif.. else

$time_hour = date("H");

if ($time_hour >= "10" && $time_hour < "12") {
  echo "Good morning!";
} elseif ($time_hour < "18") {
  echo "Good afternoon!";
} else {
  echo "Good evening!";
}

var_dump($time_hour); // string(2) "17"

Another example:

$age = 24;
if ($age === 24) echo "Your age is ".$age;
Operator Name Example Result
== Equal $x == $y Returns true if $x is equal to $y
=== Identical $x === $y Returns true if $x is equal to $y,
and they are of the same type


Example of writing if else statement with HMTL:

<?php if( is_product() ): ?>
  
  <div><a class="product-link" href="<?php echo esc_url( get_permalink() ); ?>" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></div>
  
<?php else: ?>
  
  <h3><a class="product-link" href="<?php echo esc_url( get_permalink() ); ?>" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a></h3>
  
<?php endif; ?>

Another example: https://www.php.net/manual/en/control-structures.elseif.php


ternary operator ?

$age = 24;
echo $age < 21 ? "Bellow 21 yo" : "Above 21 yo";

Another example:

$a = 5;
$b = 10;
$c = ($a < $b) ? "a is less than b"  : "a is not less than b";
echo $c; // a is less than b

Another example (Note that you need to use parenthesis for nested ternary expressions!):

function checkSign($num) {
  return $num > 0 ?
    "positive" :
    ($num < 0 ?
      "negative" :
      "zero");
}
echo checkSign(23); // positive
echo checkSign(0); // zero
echo checkSign(-2); // negative

short ternary ?:

Short ternary operator ?: will check if the variable has a falsy value (or if it does not exist), then executes.

$age = 24;
echo $age ?: 18; // 24

If $age variable was falsy, we would get:

$age = 0;
echo $age ?: 18; // 18

If $age variable was undefined, we would get a warning, but it will still echo the value ‘18’:

echo $age ?: 18;
// Warning: Undefined variable $age in C:\xampp\htdocs\tutorials\a.php on line 3
// 18

Another example:

$price;
$defaultPrice = $price ?: 15;
echo($defaultPrice);

// Warning: Undefined variable $price in C:\xampp\htdocs\tutorials\a.php on line 4
// 15

Another example (without warning - the better way):

$defaultPrice = isset($price) ?: 15;
echo($defaultPrice); // 15

null coalescing operator ??

Another example with Null coalescing operator ??

$defaultPrice = $price ?? 15;

// same as
$defaultPrice = isset($price) ?: 15;

// same as (the most readable)
$defaultPrice = isset($price) ? $price : 15;

switch case

$favcolor = "red";

switch ($favcolor) {
  case "red":
    echo "Your favorite color is red!";
    break;
  case "blue":
    echo "Your favorite color is blue!";
    break;
  case "green":
    echo "Your favorite color is green!";
    break;
  default:
    echo "Your favorite color is neither red, blue, nor green!";
}

Another example:

$message = '';
$role = 'author';

switch ($role) {
	case 'admin':
		$message = 'Welcome, admin!';
		break;
	case 'editor':
	case 'author':
		$message = 'Welcome! Do you want to create a new article?';
		break;
	case 'subscriber':
		$message = 'Welcome! Check out some new articles.';
		break;
	default:
		$message = 'You are not authorized to access this page';
}

echo $message; // Welcome! Do you want to create a new article?

PHP loops

Cat Brother May I have some Loops

while, do while

$i = 1;
while ($i <= 10):
    echo $i;
    $i++;
endwhile;

// 12345678910

Or

$i = 0;
while($i <= 100) {
  echo $i.' ';
  $i += 10;
}
// 0 10 20 30 40 50 60 70 80 90 100

Another example:

$i = 0;
while($i <= 100) {
  echo $i.' ';
  if ($i === 5) break;
  $i++;
}
// 0 1 2 3 4 5


Example with do while

$i = 1;
do {
  echo "$i ";
  $i++;
} while ($i <= 5);
// 1 2 3 4 5

for loops

for ($i = 0; $i <= 10; $i++) {
  echo "$i ";
}
// 0 1 2 3 4 5 6 7 8 9 10

for ($i = 0; $i <= 100; $i += 10) {
  echo "$i ";
}
// 0 10 20 30 40 50 60 70 80 90 100

Another example - looping over an array and initializing both $i and $mySum variables

$myArr = [9, 10, 11, 12];
for ($i = 0, $mySum = 0; $i < count($myArr); $i++) {
  $mySum += $myArr[$i];
}

echo $mySum; // 42

foreach (arrays)

The foreach loop - Loops through a block of code for each element in an array.

$colors = array("red", "green", "blue", "yellow");

foreach ($colors as $color_value) {
  echo "$color_value ";
}
// red green blue yellow

And for associative arrays:

$ages = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");

foreach($ages as $key => $value) {
  echo "$key = $value<br>";
}
/*
Peter = 35
Ben = 37
Joe = 43
*/


More examples

$todos = [
  ['title' => 'Todo title 1', 'completed' => true],
  ['title' => 'Todo title 2', 'completed' => false],
  ['title' => 'Todo title 3', 'completed' => true]
];

/* Example 1 */
foreach($todos as $key => $value) {
  echo("<pre>");
  echo($key." = ");  print_r($value);
  echo("</pre>");
}

/* Example 2 */
foreach($todos as $id => $todo) {
  if(is_array($todo)) {
    foreach($todo as $key => $val) {
      echo "$key = $val; ";
    }
    echo "<br>";
  }
}

PHP Associative Arrays

Another example:

$person = [
  'name' => 'Brad',
  'surname' => 'Traversy',
  'age' => 30,
  'hobbies' => ['Tennis', 'Video Games']
];

foreach($person as $key => $val) {
  if (is_array($val)) {
    echo "$key = " . implode(", ", $val) . "<br>";
  } else {
    echo "$key = $val<br>";
  }
}

PHP Associative Arrays


PHP Functions

More about functions and strict_types on w3schools

function getTodayDateFormatted() {
  return date("l, F d, Y");
}
echo getTodayDateFormatted(); // Saturday, September 04, 2021

echo toCelsius(80); // 26.666666666667

function toCelsius($fahrenheit) {
  return (5/9) * ($fahrenheit - 32);
}

function toFahrenheit($celsius) {
  return $celsius * 9 / 5 + 32;
}

Note that functions can be called before they are declared.


Another example:

$inventory = array(
  array("name"=>"pork", "price"=>5.00),
  array("name"=>"pizza", "price"=>4.50),
  array("name"=>"milk", "price"=>1.90),
  array("name"=>"oranges", "price"=>2.10)
);

function sumOfPrices($arrOfObj) {
  $sum = 0;
  foreach($arrOfObj as $obj) {
    $sum += $obj["price"];
  }
  return $sum;
}
echo sumOfPrices($inventory); // 13.5

In JavaScript, we would have write:

// JavaScript
var inventory = [
  { name: "pork", price: 5.0 },
  { name: "pizza", price: 4.5 },
  { name: "milk", price: 1.9 },
  { name: "oranges", price: 2.1 },
];

var sum = inventory.reduce((total, item) => total + item.price, 0);
console.log(sum); // 13.5


Take all the arguments of a function and save as an array

function sum(...$nums) {
  return array_sum($nums);
}
echo sum(1,2,3,4,5,6,7,8,9); // 45


Arrow Functions in PHP 7.4, array_reduce

function sum(...$nums) {
  return array_reduce($nums, fn($carry, $n) => $carry + $n);
}
echo sum(1,2,3,4,5,6,7,8,9); // 45

Another example:

$inventory = array(
  array("name"=>"pork", "price"=>5.00),
  array("name"=>"pizza", "price"=>4.50),
  array("name"=>"milk", "price"=>1.90),
  array("name"=>"oranges", "price"=>2.10)
);
$sumPrice = array_reduce($inventory, fn($total, $arr) => $total + $arr["price"], 0);
echo($sumPrice); // 13.5

Higher order array functions

Array Reduce

Array Map

Another example

$func = function($value) {
    return $value * 2;
};

print_r(array_map($func, range(1, 5))); // [2, 4, 6, 8, 10]

Array Filter




PHP OOP

Resources on PHP OOP from w3schools:

Introduction to PHP OOP syntax

class Person {
  public $name;
  public $surname;
  private $age;
}

// To create an instance (object) of Person class
$personObj = new Person();
$personObj->name = "Radu";
$personObj->surname = "Alex";

// if we try to set a value to a private property we get Fatal Error
// $personObj->age = 24;

echo "<pre>";
var_dump($personObj);
echo "</pre>";

PHP OOP Intro


class Person {
  public $name;
  public $surname;
  private $age;

  public function __construct($name, $surname = "undefined", $age = 0) {
    $this->name = $name;
    $this->surname = $surname;
    $this->age = $age;
  }
}

$personObj = new Person('Radu', 'Alex');

echo "<pre>";
var_dump($personObj);
echo "</pre>";

/*
object(Person)#1 (3) {
  ["name"]=>
  string(4) "Radu"
  ["surname"]=>
  string(4) "Alex"
  ["age":"Person":private]=>
  int(0)
}
*/



class Person {
  public $name;
  public $surname;
  private $age;

  public function __construct($name, $surname = null, $age = null) {
    $this->name = $name;
    $this->surname = $surname;
    $this->age = $age;
  }
  public function setAge($age) {
    $this->age = $age;
  }
  public function getAge($age) {
    return $this->$age;
  }
}

$personObj = new Person('Radu', 'Alex');
$personObj->setAge(24);

echo "<pre>";
var_dump($personObj);
echo "</pre>";

/*
object(Person)#1 (3) {
  ["name"]=>
  string(4) "Radu"
  ["surname"]=>
  string(4) "Alex"
  ["age":"Person":private]=>
  int(24)
}
*/


Static properties and methods

class Person {
  public $name;
  public $surname;
  private $age;
  public static $counter = 0;

  public function __construct($name, $surname = null, $age = null) {
    $this->name = $name;
    $this->surname = $surname;
    $this->age = $age;
    self::$counter++;
  }

  public function setAge($age) {
    $this->age = $age;
  }
  public function getAge($age) {
    return $this->$age;
  }
  public static function getCounter() {
    return self::$counter;
  }
}

$personObj = new Person('James', 'May');
$personObj->setAge(58);

$personObj2 = new Person('Jeremy', 'Clarkson', 61);

echo Person::$counter; // 2
echo Person::getCounter(); // 2


Inheritance

<?php
// Person.php
class Person {
  public string $name;
  public string $surname;
  private ?int $age;
  public static int $counter = 0;

  public function __construct($name, $surname = "", $age = null) {
    $this->name = $name;
    $this->surname = $surname;
    $this->age = $age;
    self::$counter++;
  }

  public function setAge($age) {
    $this->age = $age;
  }
  public function getAge($age) {
    return $this->$age;
  }
  public static function getCounter() {
    return self::$counter;
  }
}

<?php
// Student.php
require_once "Person.php";

class Student extends Person {

}

<?php
// index.php
require_once "Person.php";
require_once "Student.php";

$personObj = new Person('Oliver', 'Doe', 32);
$studentObj = new Student('Emma', 'Doe', 28);


echo "<pre>";
var_dump($personObj);
echo "</pre>";

echo "<pre>";
var_dump($studentObj);
echo "</pre>";

PHP OOP Intro


// Student.php
require_once "Person.php";

class Student extends Person {
  public string $studentId;

  public function __construct($name, $surname, $age, $studentId) {
    parent::__construct($name, $surname, $age);
    $this->studentId = $studentId;
  }
}

// index.php
require_once "Person.php";
require_once "Student.php";

$personObj = new Person('Oliver', 'Doe', 32);
$studentObj = new Student('Emma', 'Doe', 28, 2321);


echo "<pre>";
var_dump($personObj);
echo "</pre>";

echo "<pre>";
var_dump($studentObj);
echo "</pre>";

PHP OOP Intro


Private vs Protected access specifiers

Public/Protected/Private are called access specifiers or access modifiers.




PHP Files

Including PHP files with include, require

Let’s simulate two pages of a website, having index.php and about.php files.

<!-- index.php -->
<body>
  <nav>
    <a href="index.php">Home</a>
    <a href="about.php">About</a>
  </nav>

  <h1>Homepage</h1>
</body>

<!-- about.php -->
<body>
  <nav>
    <a href="index.php">Home</a>
    <a href="about.php">About</a>
  </nav>

  <h1>About us</h1>
</body>

But, instead of having repetitive code (in this case the menu with <nav> element), we can store the HTML elements (or JS scripts) in another php file (in this example header.php), which we will access from both index.php and about.php.

We will create a folder called partials where we will have the /partials/header.php file.

<!-- /partials/header.php -->
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Tutorial</title>
</head>

<body>
<header>
  <nav>
    <ul>
      <li><a href="index.php">Home</a></li>
      <li><a href="about.php">About</a></li>
    </ul>
  </nav>
</header>

Then, on both index.php and about.php we will write at the beginning:

<?php include "partials/header.php"; ?>

<h1>Homepage</h1>
</body>

PHP Including PHP Files

The difference between include() and require() in PHP is that… if we use include() to include a file that doesn’t actually exists, then the PHP will give us a warning that the file was not found, but it will continue to execute the rest of the code.

require() will stop the execution of entire PHP file if the file that we are trying to include is not found -> it will give us a Fatal error.

There are also include_once and require_once parameters. If we require/include a file multiple times, it will get included multiple times. include_once/require_once will stop that from happening.

PHP Including PHP Files


We can also create a partials/footer.php where we add <footer> element and we close the </body>,

<!-- /partials/footer.php -->

<footer>
  Copyright &copy; <?php echo date("Y");?> Radu B. All rights reserved.
</footer>
</body>

<!-- index.php -->

<?php require_once "partials/header.php"; ?>

<h1>Homepage</h1>

<?php require_once "partials/footer.php"; ?>

<!-- about.php -->

<?php require_once "partials/header.php"; ?>

<h1>About us</h1>

<?php require_once "partials/footer.php"; ?>

Also, we can write php files with functions in them, and include the files in other php files where we can call the functions.

Example:

<?php
/* /functions/calculate.php */

function calculatePrice($price, $taxes) {
  if (empty($taxes)) $taxes = 0.05;
  return $price * (1 + $taxes);
}

<?php
/* index.php */

require_once "functions/calculate.php";

echo calculatePrice(100, 0.19); // 119


Working with File system

References from w3schools:


But first, let’s explore some definitions:

Magic constants

Magic constants = constants that change their value based on the execution of context.

echo __DIR__; // C:\xampp\htdocs\tutorials\phpTutorial
echo __FILE__; // C:\xampp\htdocs\tutorials\phpTutorial\index.php
echo __LINE__; // 8 -- this prints the current line number in the current file

Other magic constants unrelated to files:

See more PHP Predefined constants.

Create, rename, delete directory with PHP

We can create directories (folders) on server with mkdir('directory_name', 0755); (where 0755 represents the permissions).

// Create directory
mkdir('new_dir', 0777);

// Rename directory
rename('new_dir', "new_dir_v2");

// Delete directory
rmdir('new_dir_v2');


Create files, Read files

(Notes from w3schools)

The readfile() function reads a file and writes it to the output buffer. The readfile() function is useful if all you want to do is open up a file and read its contents.

The fopen() function is a better method to open files. This function gives you more options than the readfile() function.

The fopen() function is also used to create a file. Maybe a little confusing, but in PHP, a file is created using the same function used to open files. If you use fopen() on a file that does not exist, it will create it, given that the file is opened for writing (w) or appending (a).

Modes for fopen Description
r Open a file for read only. File pointer starts at the beginning of the file
w Open a file for write only. Erases the contents of the file or creates a new file if it doesn’t exist. File pointer starts at the beginning of the file
a Open a file for write only. The existing data in file is preserved. File pointer starts at the end of the file. Creates a new file if the file doesn’t exist
x Creates a new file for write only. Returns FALSE and an error if file already exists
r+ Open a file for read/write. File pointer starts at the beginning of the file
w+ Open a file for read/write. Erases the contents of the file or creates a new file if it doesn’t exist. File pointer starts at the beginning of the file
a+ Open a file for read/write. The existing data in file is preserved. File pointer starts at the end of the file. Creates a new file if the file doesn’t exist
x+ Creates a new file for read/write. Returns FALSE and an error if file already exists


Another method to get a file and retrieve its content is with file_get_contents('lorem.txt').


Examples:

<?php
echo file_get_contents("webdictionary.txt");

echo readfile("webdictionary.txt");

file_put_contents("newly_created_file.txt", "Some content"); // creates and appends "Some content"

echo readfile("newly_created_file.txt"); // Some content

unlink("newly_created_file.txt"); // deletes newly_created_file.txt

<?php
$myfile = fopen("webdictionary.txt", "r") or die("Unable to open file!");
echo fread($myfile, filesize("webdictionary.txt"));
fclose($myfile);

The first parameter of fread() contains the name of the file to read from and the second parameter specifies the maximum number of bytes to read.

The fclose() function is used to close an open file.

<?php
$myfile = fopen("webdictionary.txt", "r");
// some code to be executed....
fclose($myfile);
?>


More examples:

<?php
$myfile = fopen("webdictionary.txt", "r") or die("Unable to open file!");
// Output one line until end-of-file
while(!feof($myfile)) {
  echo fgets($myfile) . "<br>";
}
fclose($myfile);

The feof() function checks if the “end-of-file” (EOF) has been reached.

The feof() function is useful for looping through data of unknown length.

Another example: Download a file from another server and put it on your server:

<?php
$url_to_file = "http://staging.testserver.com/website-archive.tgz";
$new_filename = "website-archive-2021-09-12.tgz";

file_put_contents($new_filename, fopen($url_to_file, 'r') );

echo "The file ". $new_filename ." has been uploaded to your server!";


Read files and folders inside a directory with scandir()

$files = scandir('./');

echo "<pre>";
var_dump($files);
echo "</pre>";

/*
array(5) {
  [0]=>
  string(1) "."
  [1]=>
  string(2) ".."
  [2]=>
  string(9) "about.php"
  [3]=>
  string(9) "index.php"
  [4]=>
  string(8) "partials"
}
*/


More useful functions:

file_exists('sample.txt'); // true / false

is_dir('test'); // false if a directory named 'test' doesn't exist in the same folder as this file

filemtime('test.txt'); // file modification time

filesize('test.txt');

ALL OF THESE FUCTIONS AND MORE HERE - php manual filesystem.


Read JSON files from API

$usersJson = file_get_contents("https://jsonplaceholder.typicode.com/users");

echo($usersJson); // returns a string of 5645 characters...

We can convert the retrieved JSON into an array using json_decode():

$usersJson = file_get_contents("https://jsonplaceholder.typicode.com/users");

echo "<pre>";
var_dump(json_decode($usersJson));
echo "</pre>";

PHP Retrieve JSON file

We can also specify if we want to convert the elements in the main array as associative arrays with key-value pairs (by default the element within main array are objects - the second parameter is false by default):

$usersJson = file_get_contents("https://jsonplaceholder.typicode.com/users");
$users = json_decode($usersJson, true);

echo "<pre>";
var_dump($users);
echo "</pre>";

PHP Retrieve JSON file


File upload from HTML Form

PHP File Upload from HTML Form




PHP cURL

cURL (a client for URLs) is a library that lets you make HTTP requests in PHP. Or, cURL is a tool that gives us the possibility to interact (remotely) with other services (eg. with an API).

cURL is very powerful in retrieving data from API, making POST request to APIs, uploading and downloading files, and authentication.


Here’s a fast simple cURL example from

// Initialize a connection with cURL (ch = cURL handle, or "channel")
$ch = curl_init();

// Set the URL
curl_setopt($ch, CURLOPT_URL, 'http://www.example.com');

// Set the HTTP method
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'GET');

// Return the response instead of printing it out
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

// Send the request and store the result in $response
$response = curl_exec($ch);

echo 'HTTP Status Code: ' . curl_getinfo($ch, CURLINFO_HTTP_CODE) . PHP_EOL;
echo 'Response Body: ' . $response . PHP_EOL;

// Close cURL resource to free up system resources
curl_close($ch);

PHP cURL Introduction

Make a simple cURL request

$url = "https://jsonplaceholder.typicode.com/users";
$resource = curl_init($url);
curl_setopt($resource, CURLOPT_RETURNTRANSFER, true);
$result = curl_exec($resource);

echo "<pre>";
var_dump($result);
echo "</pre>";
// returns a string of 5645 characters long...

PHP Retrieve JSON file with cURL


Retrieve cURL status code

$url = "https://jsonplaceholder.typicode.com/users";
$resource = curl_init($url);
curl_setopt($resource, CURLOPT_RETURNTRANSFER, true);
$result = curl_exec($resource);

$status_code = curl_getinfo($resource, CURLINFO_HTTP_CODE);

echo "<pre>";
var_dump($status_code);
echo "</pre>";

curl_close($resource);

// echo "<pre>";
// var_dump($result);
// echo "</pre>";

PHP Retrieve JSON file

PHP Retrieve JSON file with cURL and get status code


POST request with cURL

$url = "https://jsonplaceholder.typicode.com/users";
$resource = curl_init();

$user = [
  'name' => 'Johnny Doe',
  'username'=> 'john',
  'email' => `john.doe@example.com`
];
curl_setopt_array($resource, [
  CURLOPT_URL => $url,
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_POST => true,
  CURLOPT_HTTPHEADER => ['content-type: application/json'],
  CURLOPT_POSTFIELDS => json_encode($user)
]);

$result = curl_exec($resource);
$status_code = curl_getinfo($resource, CURLINFO_HTTP_CODE);

curl_close($resource);



echo "<pre>";
var_dump($status_code);
echo "</pre>";

echo "<pre>";
var_dump($result);
echo "</pre>";

PHP Retrieve JSON file with cURL and get status code



(Optional) Interesting observation when using cURL to POST data from here: https://www.php.net/manual/en/curl.examples-basic.php

It is important to notice that when using curl to post form data and you use an array for CURLOPT_POSTFIELDS option, the post will be in multipart format

<?php
$params=['name'=>'John', 'surname'=>'Doe', 'age'=>36)
$defaults = array(
  CURLOPT_URL => 'http://myremoteservice/',
  CURLOPT_POST => true,
  CURLOPT_POSTFIELDS => $params,
);

$ch = curl_init();
curl_setopt_array($ch, ($options + $defaults));
curl_close($ch);
?>

This produce the following post header:

--------------------------fd1c4191862e3566
Content-Disposition: form-data; name="name"

John
--------------------------fd1c4191862e3566
Content-Disposition: form-data; name="surnname"

Doe
--------------------------fd1c4191862e3566
Content-Disposition: form-data; name="age"

36
--------------------------fd1c4191862e3566--

You need to set CURLOPT_POSTFIELDS as follow to produce a standard post header

CURLOPT_POSTFIELDS => http_build_query($params),

// Which is:
// name=John&surname=Doe&age=36

This caused me 2 days of debug while interacting with a java service which was sensible to this difference, while the equivalent one in PHP got both format without problem.

Retrieve HTML from a website and save into file

Example: Using PHP’s cURL module to fetch the example.com HTML homepage

<?php
// Initialize a connection with cURL (ch = cURL handle, or "channel")
$ch = curl_init("http://www.example.com/");
$fp = fopen("example_homepage.txt", "w");

curl_setopt($ch, CURLOPT_FILE, $fp);
curl_setopt($ch, CURLOPT_HEADER, 0);

curl_exec($ch);
if(curl_error($ch)) {
    fwrite($fp, curl_error($ch));
}
curl_close($ch);
fclose($fp);

PHP Retrieve JSON file with cURL and get status code

^^ This can also be used to download files (from another server) and save them on your server.


More examples here: 5 PHP cURL examples that includes:

  1. Downloading the content of a website
  2. Downloading a file from a website
  3. Auto form submission
  4. Authentication
  5. Use of cookies

Web scraping with PHP?




This site is open source. Improve this page.