What is overloading and overriding php?

Strictly speaking, there's no difference, since you cannot do either :)

Function overriding could have been done with a PHP extension like APD, but it's deprecated and afaik last version was unusable.

Function overloading in PHP cannot be done due to dynamic typing, ie, in PHP you don't "define" variables to be a particular type. Example:

$a=1;
$a='1';
$a=true;
$a=doSomething();

Each variable is of a different type, yet you can know the type before execution (see the 4th one). As a comparison, other languages use:

int a=1;
String s="1";
bool a=true;
something a=doSomething();

In the last example, you must forcefully set the variable's type (as an example, I used data type "something").

Another "issue" why function overloading is not possible in PHP: PHP has a function called func_get_args(), which returns an array of current arguments, now consider the following code:

function hello($a){
  print_r(func_get_args());
}

function hello($a,$a){
  print_r(func_get_args());
}

hello('a');
hello('a','b');

Considering both functions accept any amount of arguments, which one should the compiler choose?

Finally, I'd like to point out why the above replies are partially wrong; function overloading/overriding is NOT equal to method overloading/overriding.

Where a method is like a function but specific to a class, in which case, PHP does allow overriding in classes, but again no overloading, due to language semantics.

To conclude, languages like Javascript allow overriding (but again, no overloading), however they may also show the difference between overriding a user function and a method:

/// Function Overriding ///

function a(){
   alert('a');
}
a=function(){
   alert('b');
}

a(); // shows popup with 'b'


/// Method Overriding ///

var a={
  "a":function(){
    alert('a');
  }
}
a.a=function(){
   alert('b');
}

a.a(); // shows popup with 'b'

Function Overloading in PHP

Function overloading is a feature that permits making creating several methods with a similar name that works differently from one another in the type of the input parameters it accepts as arguments.

Example

Let us now see an example to implement function overloading−

 Live Demo

<?php
   class Shape {
      const PI = 3.142 ;
      function __call($name,$arg){
         if($name == 'area')
            switch(count($arg)){
               case 0 : return 0 ;
               case 1 : return self::PI * $arg[0] ;
               case 2 : return $arg[0] * $arg[1];
            }
      }
   }
   $circle = new Shape();
   echo $circle->area(3);
   $rect = new Shape();
   echo $rect->area(8,6);
?>

Output

This will produce the following output−

9.42648

Function Overriding in PHP

In function overriding, the parent and child classes have the same function name with and number of arguments

Example

Let us now see an example to implement function overriding−

 Live Demo

<?php
   class Base {
      function display() {
         echo "\nBase class function declared final!";
      }
      function demo() {
         echo "\nBase class function!";
      }
   }
   class Derived extends Base {
      function demo() {
         echo "\nDerived class function!";
      }
   }
   $ob = new Base;
   $ob->demo();
   $ob->display();
   $ob2 = new Derived;
   $ob2->demo();
   $ob2->display();
?>

Output

This will produce the following output−

Base class function!
Base class function declared final!
Derived class function!
Base class function declared final!

Updated on 02-Jan-2020 06:36:33

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