What is PHP function overloading for?

Question

In languages like Java, overloading can be used in this way:

void test($foo, $bar){}
int test($foo){}

Then if you called test()

Answer 1

If you want to overload a function like in Java, don’t specify any arguments and use the func_num_args and func_get_args function to get the number of arguments or the arguments themselves that were passed to that function:

function test() {
    $args = func_get_args();
    switch (count($args)) {
        case 1:
            // one argument passed
            break;
        case 2:
            // two arguments passed
            break;
        default:
            // illegal numer of arguments
            break;
    }
}

Answer 2

PHP's meaning of overloading is different than Java's. In PHP, overloading means that you are able to add object members at runtime, by implementing some of the __magic methods, like __get, __set, __call, __callStatic. You load objects with new members.

Overloading in PHP provides means to dynamically "create" properties and methods. These dynamic entities are processed via magic methods one can establish in a class for various action types.

An example:

class Foo
{
    public function __call($method, $args)
    {
        echo "Called method $method";
    }
}

$foo = new Foo;

$foo->bar(); // Called method bar
$foo->baz(); // Called method baz

And by the way, PHP supports this kind of overloading since PHP 4.3.0. The only difference is that in versions prior to PHP 5 you had to explicitly activate overloading using the overload() function.

Answer 3

To over load a function simply do pass parameter as null by default,

class ParentClass
{
   function mymethod($arg1 = null, $arg2 = null, $arg3 = null)  
   {  
     if( $arg1 == null && $arg2 == null && $arg3 == null ){ 
        return 'function has got zero parameters <br />';
     }
     else{
       $str = '';
       if( $arg1 != null ) 
        $str .= "arg1 = ".$arg1." <br />";

       if( $arg2 != null ) 
        $str .= "arg2 = ".$arg2." <br />";

       if( $arg3 != null ) 
        $str .= "arg3 = ".$arg3." <br />";

       return $str;
      }
   }
}

// and call it in order given below ...

$obj = new ParentClass;

echo '<br />$obj->mymethod()<br />';
echo $obj->mymethod();

echo '<br />$obj->mymethod(null,"test") <br />';
echo $obj->mymethod(null,'test');

echo '<br /> $obj->mymethod("test","test","test")<br />';
echo $obj->mymethod('test','test','test');