Overloading and Overriding in PHP

Function or method Overloading and overriding method is very basic and useful feature of any oop language. In this tutorial we will discuss implementation of method overloading and overriding in php.  Here first we will explore basics of overloading and overriding. After exploration of basics we will implement overloading and overriding in php. Before going further I am assuming that you have basic knowledge of classes and inheritance in php. Also you have understanding about magic method in php. Magic method because overloading in php can be implmented using magic methods.

What is Method Overriding in OOP ?

Basic meaning of overriding in oop is same as real word meaning. In real word meaning of overriding  phenomena of replacing the same parental behavior in child. This is same in case of method overriding in oop. In oop meaning of overriding is to replace parent class method in child class. Or in simple technical word method overriding mean changing behavior of the method. In oop overriding is process by which you can re-declare your parent class method in child class. So basic meaning of overriding in oop is to change behavior of your parent class method.

Normally method overriding required when your parent class have some method, but in your child class you want the same method with different behavior. By overriding of method you can complete change its behavior from parent class. To implment method overiding in oop we commonly create same method in child class.

What is Method Overloading in OOP ?

Overloading in oop is same as overloading in real word. In real word overloading means assigning extra work to same machine or person. In oop method overloading is same. By process of method overloading you are asking your method to some extra work. Or in some cases we can say some different work also.

Normally method overloading in oop is managed on the basis of the argument passed in function. We can achieve overloading in oop by providing different argument in same function.

Overloading and Overriding in PHP

Hope your basic concept of overloading and overriding is clear now. Now let us explore implementation of overloading and overriding in php.

Implementation of overriding in php is very easy. If your parent class has a function. You can create function with same name in your child class to override the function. Implementation of overriding can not be achieved by creating 2 function with same name and different argument in php. Because we can not create same name function more than 1 time in php class. To implement overloading we need to take help of magic method in php. In below section we will explore overloading and overriding one by one.

Overloading in PHP

As we know that we can not implement overloading by create 2 function in with same name in class. So to implement overloading in php we will take help of magic method __call. Magic method __call invoked when method called by class object is not available in class. So here we will not create method exactly and will take help of __call method. Now call method will provide us 2 argument, 1st name of the method called and parameter of the function. Now with the help of either switch case or if else we will implement overloading in php. Following is very simple example of overloading in php.

class test
{
public function __construct()
{
//Your logic for constructor
}
public function __call($method_name , $parameter)
{
if($method_name == "overlodedFunction") //Function overloading logic for function name overlodedFunction
{
$count = count($parameter);
switch($count)
{
case "1":
//Business log in case of overlodedFunction function has 1 argument
echo "You are passing 1 argument";
break;
case "2": //Incase of 2 parameter
echo "You are passing 2 parameter";
break;
default:
throw new exception("Bad argument");
}
}
else
{
throw new exception("Function $method_name does not exists ");
}
}
}
$a = new test();
$a->overlodedFunction("ankur");
$a->overlodedFunction("techflirt" , "ankur");

As in above class test magic method __call is implemented which is managing overloading

public function __call($method_name , $parameter)
{
if($method_name == "overlodedFunction") //Function overloading logic for function name overlodedFunction
{
$count = count($parameter);
switch($count)
{
case "1":
//Business log in case of overlodedFunction function has 1 argument
echo "You are passing 1 argument";
break;
case "2": //Incase of 2 parameter
echo "You are passing 2 parameter";
break;
default:
throw new exception("Bad argument");
}
}
else
{
throw new exception("Function $method_name does not exists ");
}
}

As we know that __call magic method invoked when method is not available in the class. So in case of above test class example we have not created function overlodedFunction. So whenever method overlodedFunction is called __call invoked. __call pass 2 variable, first  name of the called method and other is parameter passed in the called function.

Now in the __call function I have applied if condition to ensure that our business logic of overloading works only for overlodedFunction function. In if block we have counted number of argument in parameter and applied business logic.

Overriding in PHP

Overriding in php is very easy. As we know that overriding is process of modifying the inherited method. So in case of inheritance you only need to create method with same name in your child class which you want to override. Following is example of overriding of method in php.

class testParent
{
public function f1()
{
echo 1;
}
public function f2()
{
echo 2;
}
}
class testChild
{
function f2($a) //overriding function f2
{
echo "$a";
}
}
$a = new testChild();
$a->f2("ankur");//it will print ankur

In above example you are overriding function f2. While overriding you are free to change business logic, visibility and number of parameter.

Magic Methods in PHP

Magic methods in php are some predefined function by php compiler which executes on some event. Magic methods starts with prefix __, for example __call, __get, __set. I am including magic methods topic in my oop tutorial here because these method mostly applied in classes of PHP. If you have gone through my previous chapter then you have seen __construct function. __construct is a magic method which automatically call on creating object of the classes. There are verous magic methods in php. Here we will discuss some of the most comman magic methods of php which will be use in object oriented programming. First of let us review all magic method with short description.

 

List of List of Magic Methods in PHP

Magic Method Description
__construct This magic methods is called when someone create object of your class. Usually this is used for creating constructor in php5.
__destruct This magic method is called when object of your class is unset. This is just opposite of __construct.
__get This method called when your object attempt to read property or variable of the class which is inaccessible or unavailable.
__set This method called when object of your class attempts to set value of the property which is really inaccessible or unavailable in your class.
__isset This magic methods trigger when isset() function is applied on any property of the class which isinaccessible or unavailable.
__unset __unset is something opposite of isset method. This method triggers when unset() function called on inaccessible or unavailable property of the class.
__call __call magic method trigger when you are attempting to call method or function of the class which is either inaccessible or unavailable.
__callstatic __callstatic execture when inaccessible or unavailable method is in static context.
__sleep __sleep methods trigger when you are going to serialize your class object.
__wakeup __wakeup executes when you are un serializing any class object.
__toString __toString executes when you are using echo on your object.
__invoke __invoke called when you are using object of your class as function

Above list is the most conman used magic methods in php object oriented programming. Above magic methods of php executes on some specif  events occur on your class object. For example if you simply echo your object then __toString method trigger. Let us create group of related magic method and analyze how it is working.

__construct and __destruct magic method in PHP

__construct method trigger on creation of object. And __destruct triggers of deletion of object. Following is very basic example of __construct and __destruct magic method in php:
class test
{
function __construct()
{
echo 1;
}
function __destruct()
{
echo 2;
}
}
$objT = new test(); //__construct get automatically executed and print 1 on screen
unset($objT);//__destruct triggers and print 2.

__get __set __call and __callStatic Magic Methods

__get, __set, __call and __callStatic all magic methods in php directly related with no accessible method and property of the class.
__get takes one argument and executes when any inaccessible property of the method is called. It takes name of the property as argument.
__set takes two property and executes when object try to set value in inaccessible property. It take first parameter as name of the property and second as the value which object is try to set.
__call method fires when object of your class is trying to call method of property which is either non accessible or not available. It takes 2 parameter  First parameter is string and is name of function. Second parameter is an array which is arguments passed in the function.
__callStatic is a static magic method. It executes when any method of your class is called by static techniques.

Following is example of __get , __set , __call and __callStatic magic methods
class test
{
function __get($name)
{
echo "__get executed with name $name ";
}
function __set($name , $value)
{
echo "__set executed with name $name , value $value";
}
function __call($name , $parameter)
{
$a = print_r($parameter , true); //taking recursive array in string
echo "__call executed with name $name , parameter $a";
}
static function __callStatic($name , $parameter)
{
$a = print_r($parameter , true); //taking recursive array in string
echo "__callStatic executed with name $name , parameter $a";
}
}
$a = new test();
$a->abc = 3;//__set will executed
$app = $a->pqr;//__get will triggerd
$a->getMyName('ankur' , 'techflirt', 'etc');//__call willl be executed
test::xyz('1' , 'qpc' , 'test');//__callstatic will be executed

__isset and __unset magic methods

__isset and __unset magic methods in php are opposite of each other.
__isset magic methods executes when function isset() is applied on property which is not available or not defined. It takes name of the parameter as an argument.
__unset magic method triggers when unset() method is applied on the property which is either not defined or not accessible. It takes name of the parameter as an argument.
Following is example of __isset and __unset magic method in php
class test
{
function __isset($name)
{
echo "__isset is called for $name";
}
function __unset($name)
{
echo "__unset is called for $name";
}
}
$a = new test();
isset($a->x);
unset($a->c);