PHP

See the PHP Manual for more information.

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Arrays

Define an array

// Define an array.
$my_array = [a,b,c,d];

// Define an array (the old standard way < php 5.3).
$my_array = array(a,b,c,d);

Get the last element of an array

$lastEl = array_pop((array_slice($array, -1)));

Count the number of element in an array

$total = count($array);

In Object-Oriented Programming a container called a class holds a collection of functions (called methods when they are in a class). A class does nothing until an instance of it is created (instantiated). Once an instance of a class has been created the methods can be used. A program can use any number of classes.

Defining a Class

<?php
class SimpleClass
{
    // Property declaration.
    public $var = 'a default value';

    // Constant declaration.
    const VAR_NAME = 'a value';

    // Class constructor method.
    public function __construct()
    {
        echo self::VAR_NAME;
    }

    // Method declaration.
    public function displayVar() {
        echo $this->var;
    }
}
?>

Instantiate a class

PHP library classes are always at the root so simply use one slash.

// Standard class instantiation.
$my_class_instance = new MyClass();
$my_class_instance = new child\MyChildClass();
$my_class_instance = new \MyRootLevelClass();

// Instantiate a new empty class
$my_empty_class_instance = new stdClass();
$my_empty_class_instance = new (object)[]; // Optionally as of PHP 5.4

Instantiate a class dynamically

// Instantiate a class dynamically
$class_name = '\\Foo\\Bar\\MyClass';
$my_class_instance = new $class_name();

Convert an Object to an Array

$array = json_decode(json_encode($object), true);

Calling functions and methods

// Call a function programmatically
$func = 'my_function';
$func('param1'); // calls my_function('param1');

// Call a class method programmatically
$my_method_name = 'foo';
$my_class = new MyClass();
$my_class->$my_method_name(); // calls the MyClass->foo() method.

Convert an object to an array

function obj_to_array($obj)
{
    return (array) $obj;
}

Autoloading

In order to instantiate (create an instance of) a class which is defined in a separate file, that file must be included or required into the file currently being executed.

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Control Structures

Ternary Operators

$var = 5;
$var_is_greater_than_two = ($var > 2 ? true : false); // returns true.

Alt Syntax (for views)

PHP offers an alternative syntax for some of its control structures; namely, if, while, for, foreach, and switch. In each case, the basic form of the alternate syntax is to change the opening brace to a colon : and the closing brace to endif;, endwhile;, endfor;, endforeach;, or endswitch;, respectively.

<?php if ($x == 1): ?>
    ...
<?php else: ?>
    ...
<?php endif; ?>

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Filter and Sanitize

filter_input

// Sanitize input
if (is_numeric($_POST[$post_key])) {
    $filtered_db_inputs[$post_key] = filter_input(INPUT_POST, $post_key, FILTER_SANITIZE_NUMBER_INT);
} else {
    $filtered_db_inputs[$post_key] = filter_input(INPUT_POST, $post_key, FILTER_SANITIZE_STRING);
}

Trimming

Use trim, ltrim, and rtrim to remove substrings from the beginning and end of a string.

$string = ' _hello_ ';
$trimmed = trim( $string ); // Returns "_hello_"
echo trim( $trimmed, '_' ); // Returns "hello"

// Warning 'ltrim' and 'rtrim' remove all instances of all the characters passed
// to the function. It is not a string definition.
echo ltrim( $string, ' _' ); // Returns "hello_ "
echo = rtrim( $string, '_ ' ); // Returns " _hello"

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HTML and DOM Parsing

DOMDocument

PHP core comes with a very handy HTML parser called DOMDocument.
Parse html DOM with DOMDocument

// Create a new DOMDocument object.
$dom = new DOMDocument; 
 
// Load the HTML page into the object.
$dom->loadHTML($html);

// Once the HTML is loaded into the object, access nodes and child elements:

// Get an element by it's ID.
$my_div_obj = $dom->getElementById('mydiv');

// Get all elements of a type.
$anchors = $dom->getElementsByTagName('a'); 
foreach ($anchors as $anchor) {
    echo $dom->saveHTML($anchor); // Prints the text-only content of the anchor.
}

Remove HTML Tag Attribute

function remove_html_attribute($html, $attribute_name) {
    return preg_replace('/(<[^>]+)' . $attribute_name . '=".*?"/i', '$1', $html);
}

echo remove_html_attribute('<div style="color:#CCC;"></div>', 'style'); // Prints '<div></div>'

Get all image tags

preg_match_all('/]+>/i',$html, $result);