Polymorphism in PHP with Example

Polymorphism in PHP is one of the important concepts in OOPs.

Polymorphism is a Greek word. Polymorphism is created by two different words poly (means many) and morph (means forms).

It is another functionality of OOPS. In a programming language, two types of Polymorphism are there.

Function overriding (Run time Polymorphism)
Function Overloading(Compile time Polymorphism)

Function Overriding in PHP

Overriding happens only in child class.

If the parent class declares a function and the child class wants to override the parent class function then function overriding means run time polymorphism happened.

Polymorphism example in PHP

Here are taking a simple example.

Created a class parent class it has a method name().

created another class child class it inherits the feature of the parent class.

child class has also the same method name().

Defining the same method in a child is known as method overriding.

<?php
class parentclass {
    function name() {
        return 'Calling Parent name()';
    }
}
class childclass extends parentclass {
    function name() {
        return 'Calling Child name()';
    }
}
$obj = new childclass();
echo $obj->name();
echo '<hr>';
$arrobj = array();
$arrobj[0] = new parentclass;
$arrobj[1] = new childclass;
foreach ($arrobj as $key => $val) {
    echo $val->name();
    echo "<br> ";
}
//It called child function instead of parent function
?>

<?php

class parentclass {

function name() {

return 'Calling Parent name()';

}

class childclass extends parentclass {

function name() {

return 'Calling Child name()';

}

$obj = new childclass();

echo $obj->name();

echo '<hr>';

$arrobj = array();

$arrobj[0] = new parentclass;

$arrobj[1] = new childclass;

foreach ($arrobj as $key => $val) {

echo $val->name();

echo " ";

}

//It called child function instead of parent function

Output

 
Calling show method of Shape
Shape is no defined
Calling show method of Circle
Showing a Circle
Calling show method of Rectangle
Showing a Rectangle
Calling show method of Square
Showing a Square
Calling show method of Triangle
Showing a Triangle

Polymorphism example to call different methods in PHP

Here we have taken the example of Shapes.

The shape is a base class with a method shown ().

Child classes of Shape are Circle, Rectangle, Square, and Triangle.

all have an overridden method show().

<?php
class Shape {
    function show() {
        echo 'Shape is no defined<br/>';
    }
}
class Circle {
    function show() {
        echo 'Showing a Circle<br/>';
    }
}
class Rectangle {
    function show() {
        echo 'Showing a Rectangle<br/>';
    }
}
class Square {
    function show() {
        echo 'Showing a Square<br/>';
    }
}
class Triangle {
    function show() {
        echo 'Showing a Triangle<br/>';
    }
}
//creating Shape object
$objShape = new Shape();
//calling Shape method with shape object
echo ' Calling show method of Shape<br/>';
$objShape->show();
//creating Circle object
$objCircle = new Circle();
//calling Circle method with shape object
echo ' Calling show method of Circle</br>';
$objCircle->show();
//creating Rectangle object
$objRectangle = new Rectangle();
//calling Rectangle method with shape object
echo ' Calling show method of Rectangle</br>';
$objRectangle->show();
//creating Square object
$objSquare = new Square();
//calling Square method with shape object
echo ' Calling show method of Square</br>';
$objSquare->show();
$objTriangle = new Triangle();
//calling show method with shape object
echo ' Calling show method of Triangle</br>';
$objTriangle->show();
?>

<?php

class Shape {

function show() {

echo 'Shape is no defined ';

}

class Circle {

function show() {

echo 'Showing a Circle ';

}

class Rectangle {

function show() {

echo 'Showing a Rectangle ';

}

class Square {

function show() {

echo 'Showing a Square ';

}

class Triangle {

function show() {

echo 'Showing a Triangle ';

}

//creating Shape object

$objShape = new Shape();

//calling Shape method with shape object

echo ' Calling show method of Shape ';

$objShape->show();

//creating Circle object

$objCircle = new Circle();

//calling Circle method with shape object

echo ' Calling show method of Circle';

$objCircle->show();

//creating Rectangle object

$objRectangle = new Rectangle();

//calling Rectangle method with shape object

echo ' Calling show method of Rectangle';

$objRectangle->show();

//creating Square object

$objSquare = new Square();

//calling Square method with shape object

echo ' Calling show method of Square';

$objSquare->show();

$objTriangle = new Triangle();

//calling show method with shape object

echo ' Calling show method of Triangle';

$objTriangle->show();

Output

 
Calling show method of Shape
Shape is no defined
Calling show method of Circle
Showing a Circle
Calling show method of Rectangle
Showing a Rectangle
Calling show method of Square
Showing a Square
Calling show method of Triangle
Showing a Triangle

PHP Inheritance

Function Overriding in PHP

Polymorphism example in PHP

Read More