Editing PHP (section)

=== PHP objects ===
Basic [[object-oriented programming]] functionality was added in PHP&nbsp;3 and improved in PHP&nbsp;4.<ref name="The PHP Group" /> This allowed for PHP to gain further abstraction, making creative tasks easier for programmers using the language. Object handling was completely rewritten for PHP&nbsp;5, expanding the feature set and enhancing performance.<ref name="mjtsai.com" /> In previous versions of PHP, objects were handled like [[value type]]s.<ref name="mjtsai.com">{{cite web|access-date=2008-03-16|url=http://mjtsai.com/blog/2004/07/15/php-5-object-references/|title=PHP&nbsp;5 Object References |website=mjtsai.com}}</ref> The drawback of this method was that code had to make heavy use of PHP's "reference" variables if it wanted to modify an object it was passed rather than creating a copy of it. In the new approach, objects are referenced by [[handle (computing)|handle]], and not by value.{{Citation needed|date=November 2023}}

PHP&nbsp;5 introduced private and protected [[member variable]]s and methods, along with [[abstract type|abstract classes]], [[final type|final classes]], [[abstract method]]s, and [[final method]]s. It also introduced a standard way of declaring [[Constructor (computer science)|constructors]] and [[Destructor (computer science)|destructors]], similar to that of other object-oriented languages such as [[C++]], and a standard [[exception handling]] model. Furthermore, PHP&nbsp;5 added [[Interface (computing)|interfaces]] and allowed for multiple interfaces to be implemented. There are special interfaces that allow objects to interact with the runtime system. [[object (computer science)|Objects]] implementing ArrayAccess can be used with [[array data type|array]] syntax and objects implementing [[Iterator]] or [[IteratorAggregate]] can be used with the <code>foreach</code> [[language construct]]. There is no [[virtual table]] feature in the engine, so [[static variable]]s are bound with a name instead of a reference at compile time.<ref name="The PHP Group-4">{{cite web|access-date=2008-03-16|url=http://www.php.net/zend-engine-2.php|title=Classes and Objects (PHP&nbsp;5) |publisher=The PHP Group}}</ref>

If the developer creates a copy of an object using the reserved word <code>clone</code>, the Zend engine will check whether a <code>__clone()</code> method has been defined. If not, it will call a default <code>__clone()</code> which will copy the object's properties. If a <code>__clone()</code> method is defined, then it will be responsible for setting the necessary properties in the created object. For convenience, the engine will supply a function that imports the properties of the source object, so the programmer can start with a by-value [[wikt:replica|replica]] of the source object and only override properties that need to be changed.<ref>{{cite web|access-date=2008-03-16|url=https://www.php.net/language.oop5.cloning|title=Object cloning |publisher=The PHP Group}}</ref>

The [[Visibility (computer science)|visibility]] of PHP properties and methods is defined using the [[Keyword (computer programming)|keywords]] <code>public</code>, <code>private</code>, and <code>protected</code>. The default is public, if only [[variable (programming)|var]] is used; <code>var</code> is a synonym for <code>public</code>. Items declared <code>public</code> can be accessed everywhere. <code>protected</code> limits access to [[inherited class]]es (and to the class that defines the item). <code>private</code> limits visibility only to the class that defines the item.<ref>{{cite web |url=http://theserverpages.com/php/manual/en/language.oop5.visibility.php |title=Visibility (PHP Manual) |website=theserverpages.com |date=2005-05-19 |access-date=2010-08-26 |archive-date=2010-09-24 |archive-url=https://web.archive.org/web/20100924033414/http://theserverpages.com/php/manual/en/language.oop5.visibility.php |url-status=dead }}</ref> Objects of the same type have access to each other's private and protected members even though they are not the same instance.{{Citation needed|date=November 2023}}

==== Example ====
The following is a basic example of [[object-oriented programming]] in PHP&nbsp;8:

<syntaxhighlight lang="php" line>
<?php

abstract class User
{
    protected string $name;

    public function __construct(string $name)
    {
        // make first letter uppercase and the rest lowercase
        $this->name = ucfirst(strtolower($name));
    }

    public function greet(): string
    {
        return "Hello, my name is " . $this->name;
    }

    abstract public function job(): string;
}

class Student extends User
{
    public function __construct(string $name, private string $course)
    {
        parent::__construct($name);
    }

    public function job(): string
    {
        return "I learn " . $this->course;
    }
}

class Teacher extends User
{
    public function __construct(string $name, private array $teachingCourses)
    {
        parent::__construct($name);
    }

    public function job(): string
    {
        return "I teach " . implode(", ", $this->teachingCourses);
    }
}

$students = [
    new Student("Alice", "Computer Science"),
    new Student("Bob", "Computer Science"),
    new Student("Charlie", "Business Studies"),
];

$teachers = [
    new Teacher("Dan", ["Computer Science", "Information Security"]),
    new Teacher("Erin", ["Computer Science", "3D Graphics Programming"]),
    new Teacher("Frankie", ["Online Marketing", "Business Studies", "E-commerce"]),
];

foreach ([$students, $teachers] as $users) {
    echo $users[0]::class . "s:\n";

    array_walk($users, function (User $user) {
        echo "{$user->greet()}, {$user->job()}\n";
    });
}
</syntaxhighlight>

This program outputs the following:

{{samp|Students:<br>
Hello, my name is Alice, I learn Computer Science<br>
Hello, my name is Bob, I learn Computer Science<br>
Hello, my name is Charlie, I learn Business Studies<br>
Teachers:<br>
Hello, my name is Dan, I teach Computer Science, Information Security<br>
Hello, my name is Erin, I teach Computer Science, 3D Graphics Programming<br>
Hello, my name is Frankie, I teach Online Marketing, Business Studies, E-commerce|style=padding-left:0px; overflow-x: hidden; word-wrap: break-word;}}
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