How to Use the Parent Keyword in PHP: Syntax and Examples

In PHP, the parent keyword is used inside a child class to call a method or access a property from its parent class. It helps you reuse or extend functionality by referring to the parent class's version of a method or constructor.

Syntax

The parent keyword is used with the scope resolution operator :: to call a parent class method or constructor from a child class.

• parent::methodName() calls a method from the parent class.
• parent::__construct() calls the parent class constructor.

php

<?php
class ParentClass {
    public function greet() {
        echo "Hello from Parent!\n";
    }

    public function __construct() {
        echo "Parent constructor called.\n";
    }
}

class ChildClass extends ParentClass {
    public function greet() {
        parent::greet(); // Calls parent method
        echo "Hello from Child!\n";
    }

    public function __construct() {
        parent::__construct(); // Calls parent constructor
        echo "Child constructor called.\n";
    }
}
?>

Example

This example shows how a child class uses parent to call the parent class constructor and a method. It demonstrates extending behavior while reusing parent code.

php

<?php
class Animal {
    public function __construct() {
        echo "Animal created.\n";
    }

    public function sound() {
        echo "Some generic animal sound.\n";
    }
}

class Dog extends Animal {
    public function __construct() {
        parent::__construct(); // Call Animal constructor
        echo "Dog created.\n";
    }

    public function sound() {
        parent::sound(); // Call Animal sound
        echo "Bark!\n";
    }
}

$dog = new Dog();
$dog->sound();
?>

Output

Animal created.
Dog created.
Some generic animal sound.
Bark!

Common Pitfalls

Common mistakes when using parent include:

• Calling parent outside a class that extends another class causes an error.
• Forgetting to use parent:: with the scope resolution operator.
• Trying to access private parent methods or properties with parent will fail because private members are not accessible in child classes.

php

<?php
class Base {
    private function secret() {
        echo "Secret\n";
    }
}

class Derived extends Base {
    public function reveal() {
        // parent::secret(); // This will cause a fatal error because secret() is private
        echo "Cannot access private method of parent.\n";
    }
}

$obj = new Derived();
$obj->reveal();
?>

Output

Cannot access private method of parent.

Quick Reference

Usage	Description	Example
Call parent method	Calls a method from the parent class	parent::methodName()
Call parent constructor	Calls the parent class constructor	parent::__construct()
Access parent property	Access a protected or public property from parent	$this->property (no parent keyword)
Invalid access	Cannot access private parent members	parent::privateMethod() causes error

Key Takeaways

Use parent::methodName() to call a parent class method inside a child class.

Call the parent constructor with parent::__construct() to initialize inherited properties.

The parent keyword only works inside classes that extend another class.

You cannot access private methods or properties of the parent class using parent.

Always use the scope resolution operator :: with parent.