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Cheatsheet Oop PHP

This document discusses classes and objects in PHP. It explains that a class can inherit from another using the "extends" keyword. A constructor method is automatically called when an object is instantiated using the "__construct" method. Classes define functions as methods and variables as properties, which can have public, protected, or private visibility. Classes are instantiated into objects using the "new" keyword to access public members with the object operator "->".

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Cheatsheet Oop PHP

This document discusses classes and objects in PHP. It explains that a class can inherit from another using the "extends" keyword. A constructor method is automatically called when an object is instantiated using the "__construct" method. Classes define functions as methods and variables as properties, which can have public, protected, or private visibility. Classes are instantiated into objects using the "new" keyword to access public members with the object operator "->".

Uploaded by

Saw' cen
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Cheatsheets / Learn PHP

Classes and Objects in PHP


PHP extends keyword
In PHP, to de�ne a class that inherits from another, we
use the keyword extends : // Dog class inherits from Pet class.
class Dog extends Pet {
class ChildClass extends function bark() {
ParentClass {
return "woof";
}
}
}

The newly de�ned class can access members with


public and protected visibility from the base class, but
cannot access private members.
The newly de�ned class can also rede�ne or override
class members.

PHP Constructor Method


A constructor method is one of several magic methods
provided by PHP. This method is automatically called // constructor with no arguments:
when an object is instantiated. A constructor method is class Person {
de�ned with the special method name __construct . The public $favorite_color;
constructor can be used to initialize an object’s function __construct() {
properties.
$this->favorite_color = "blue";
}
}

// constructor with arguments:


class Person {
public $favorite_color;
function __construct($color) {
$this->favorite_color = $color;
}
}

1 of 2 5/11/2022, 1:09 PM
Firefox https://www.codecademy.com/learn/learn-php/modules/classes-and-objec...

PHP class
In PHP, classes are de�ned using the class keyword.
Functions de�ned within a class become methods and // Test class
variables within the class are considered properties. class Test {
There are three levels of visibility for class members: public $color = "blue";
protected $shape = "sphere";
public (default) - accessible from outside of the
private $quantity = 10;
class
public static $number = 42;
protected - only accessible within the class or its public static function returnHello() {
descendants
return "Hello";
private - only accessible within the de�ning class }
}
Members can be de�ned to be static:

Static members are accessed using the Scope


// instantiate new object
Resolution Operator ( :: ) $object = new Test();

Classes are instantiated into objects using the new // only color can be accessed from the
keyword. Members of an object are accessed using the instance
Object Operator ( -> ). echo $object->color; # Works
echo $object->shape; # Fails
echo $object->quantity; # Fails
echo $object->number; # Fails

// we use the static class to access


number
echo Test::$number;

2 of 2 5/11/2022, 1:09 PM

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