PHP function overloading

Question

You cannot overload PHP functions. Function signatures are based only on their names and do not include argument lists, so you cannot have two functions with the same name. Class method overloading is different in PHP than in many other languages. PHP uses the same word but it describes a different pattern.

You can, however, declare a variadic function that takes in a variable number of arguments. You would use func_num_args() and func_get_arg() to get the arguments passed, and use them normally.

For example:

function myFunc() {
    for ($i = 0; $i < func_num_args(); $i++) {
        printf("Argument %d: %s\n", $i, func_get_arg($i));
    }
}

/*
Argument 0: a
Argument 1: 2
Argument 2: 3.5
*/
myFunc('a', 2, 3.5);

PHP doesn't support traditional method overloading, however one way you might be able to achieve what you want, would be to make use of the __call magic method:

class MyClass {
    public function __call($name, $args) {

        switch ($name) {
            case 'funcOne':
                switch (count($args)) {
                    case 1:
                        return call_user_func_array(array($this, 'funcOneWithOneArg'), $args);
                    case 3:
                        return call_user_func_array(array($this, 'funcOneWithThreeArgs'), $args);
                 }
            case 'anotherFunc':
                switch (count($args)) {
                    case 0:
                        return $this->anotherFuncWithNoArgs();
                    case 5:
                        return call_user_func_array(array($this, 'anotherFuncWithMoreArgs'), $args);
                }
        }
    }

    protected function funcOneWithOneArg($a) {

    }

    protected function funcOneWithThreeArgs($a, $b, $c) {

    }

    protected function anotherFuncWithNoArgs() {

    }

    protected function anotherFuncWithMoreArgs($a, $b, $c, $d, $e) {

    }

}

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');

It may be hackish to some, but I learned this way from how Cakephp does some functions and have adapted it because I like the flexibility it creates

The idea is you have different type of arguments, arrays, objects etc, then you detect what you were passed and go from there

function($arg1, $lastname) {
    if(is_array($arg1)){
        $lastname = $arg1['lastname'];
        $firstname = $arg1['firstname'];
    } else {
        $firstname = $arg1;
    }
    ...
}

<?php   
/*******************************
 * author  : [email protected] 
 * version : 3.8
 * create on : 2017-09-17
 * updated on : 2020-01-12
 * download example:  https://github.com/hishamdalal/overloadable
 *****************************/

#> 1. Include Overloadable class

class Overloadable
{
    static function call($obj, $method, $params=null) {
        $class = get_class($obj);
        // Get real method name
        $suffix_method_name = $method.self::getMethodSuffix($method, $params);

        if (method_exists($obj, $suffix_method_name)) {
            // Call method
            return call_user_func_array(array($obj, $suffix_method_name), $params);
        }else{
            throw new Exception('Tried to call unknown method '.$class.'::'.$suffix_method_name);
        }
    }

    static function getMethodSuffix($method, $params_ary=array()) {
        $c = '__';
        if(is_array($params_ary)){
            foreach($params_ary as $i=>$param){
                // Adding special characters to the end of method name 
                switch(gettype($param)){
                    case 'array':       $c .= 'a'; break;
                    case 'boolean':     $c .= 'b'; break;
                    case 'double':      $c .= 'd'; break;
                    case 'integer':     $c .= 'i'; break;
                    case 'NULL':        $c .= 'n'; break;
                    case 'object':
                        // Support closure parameter
                        if($param instanceof Closure ){
                            $c .= 'c';
                        }else{
                            $c .= 'o'; 
                        }
                    break;
                    case 'resource':    $c .= 'r'; break;
                    case 'string':      $c .= 's'; break;
                    case 'unknown type':$c .= 'u'; break;
                }
            }
        }
        return $c;
    }
    // Get a reference variable by name
    static function &refAccess($var_name) {
        $r =& $GLOBALS["$var_name"]; 
        return $r;
    }
}
//----------------------------------------------------------
#> 2. create new class
//----------------------------------------------------------

class test 
{
    private $name = 'test-1';

    #> 3. Add __call 'magic method' to your class

    // Call Overloadable class 
    // you must copy this method in your class to activate overloading
    function __call($method, $args) {
        return Overloadable::call($this, $method, $args);
    }

    #> 4. Add your methods with __ and arg type as one letter ie:(__i, __s, __is) and so on.
    #> methodname__i = methodname($integer)
    #> methodname__s = methodname($string)
    #> methodname__is = methodname($integer, $string)

    // func(void)
    function func__() {
        pre('func(void)', __function__);
    }
    // func(integer)
    function func__i($int) {
        pre('func(integer '.$int.')', __function__);
    }
    // func(string)
    function func__s($string) {
        pre('func(string '.$string.')', __function__);
    }    
    // func(string, object)
    function func__so($string, $object) {
        pre('func(string '.$string.', '.print_r($object, 1).')', __function__);
        //pre($object, 'Object: ');
    }
    // func(closure)
    function func__c(Closure $callback) {
        
        pre("func(".
            print_r(
                array( $callback, $callback($this->name) ), 
                1
            ).");", __function__.'(Closure)'
        );
        
    }   
    // anotherFunction(array)
    function anotherFunction__a($array) {
        pre('anotherFunction('.print_r($array, 1).')', __function__);
        $array[0]++;        // change the reference value
        $array['val']++;    // change the reference value
    }
    // anotherFunction(string)
    function anotherFunction__s($key) {
        pre('anotherFunction(string '.$key.')', __function__);
        // Get a reference
        $a2 =& Overloadable::refAccess($key); // $a2 =& $GLOBALS['val'];
        $a2 *= 3;   // change the reference value
    }
    
}

//----------------------------------------------------------
// Some data to work with:
$val  = 10;
class obj {
    private $x=10;
}

//----------------------------------------------------------
#> 5. create your object

// Start
$t = new test;

#> 6. Call your method

// Call first method with no args:
$t->func(); 
// Output: func(void)

$t->func($val);
// Output: func(integer 10)

$t->func("hello");
// Output: func(string hello)

$t->func("str", new obj());
/* Output: 
func(string str, obj Object
(
    [x:obj:private] => 10
)
)
*/

// call method with closure function
$t->func(function($n){
    return strtoupper($n);
});

/* Output:
func(Array
(
    [0] => Closure Object
        (
            [parameter] => Array
                (
                    [$n] => 
                )

        )

    [1] => TEST-1
)
);
*/

## Passing by Reference:

echo '<br><br>$val='.$val;
// Output: $val=10

$t->anotherFunction(array(&$val, 'val'=>&$val));
/* Output:
anotherFunction(Array
(
    [0] => 10
    [val] => 10
)
)
*/

echo 'Result: $val='.$val;
// Output: $val=12

$t->anotherFunction('val');
// Output: anotherFunction(string val)

echo 'Result: $val='.$val;
// Output: $val=36







// Helper function
//----------------------------------------------------------
function pre($mixed, $title=null){
    $output = "<fieldset>";
    $output .= $title ? "<legend><h2>$title</h2></legend>" : "";
    $output .= '<pre>'. print_r($mixed, 1). '</pre>';
    $output .= "</fieldset>";
    echo $output;
}
//----------------------------------------------------------

What about this:

function($arg = NULL) {

    if ($arg != NULL) {
        etc.
        etc.
    }
}

In PHP 5.6 you can use the splat operator ... as the last parameter and do away with func_get_args() and func_num_args():

function example(...$args)
{
   count($args); // Equivalent to func_num_args()
}

example(1, 2);
example(1, 2, 3, 4, 5, 6, 7);

You can use it to unpack arguments as well:

$args[] = 1;
$args[] = 2;
$args[] = 3;
example(...$args);

Is equivalent to:

example(1, 2, 3);