Function handling Functions in PHP

Functions play an important role for writing different PHP scripts and I believe, it is very good and specialized approach to design any PHP applications in a way that can easily be configured on different environments.Thanks to PHP which provide functions which made developers life easy.

Let’s get dive in some useful function handling functions:

1. create_function:

It is a basic function of function handling functions.This function will create an anonymous PHP function.It returns a unique function name as a string, or FALSE if create an error.

SYNTAX:

string create_function ( string $args , string $code )

EXAMPLE:

$triangle = create_function($b,$h', 'return "triangle = " . ($b*$h)/2;');
echo $triangle(4,6);

OUTPUT: 12

2. function_exists:

This function is useful to check whether a function is defined or not.It returns true if the function has been defined

SYNTAX:

bool function_exists ( string $function_name )

EXAMPLE:

function func_test(){
    echo "Welcome";
}

if (function_exists('func_test')) {
   echo "Function is exists";
} 
else {
   echo "Function isn't exists";
}

OUTPUT: Function is exists

3. call_user_func_array:

It is one of my favorite PHP because it is very useful for us.this function call a function with an array of parameters. We can say it’s an alternate method for calling functions and a way to dynamically call functions and methods at run-time. Its returns a valid function name and false if error.

SYNTAX:

mixed call_user_func_array ( callback $callback , array $param_arr )

Generally we are calling a function like

function func_name(parameters)

so, with this We can call the function like

call_user_func_array ('function_name', array (parameter1,parameter2, ...));

EXAMPLE:

function Box($width,$height,$depth) {
   $b = $width*$height*$depth;
   echo $b;
}

call_user_func_array('Box', array('width' => $w, 'height' => $h, 'depth' => $d));

4. call_user_func:

This is the interesting function in function handling functions and its call a user defined function given by the first parameter. It is useful to call a function whose name you will not know until runtime.

SYNTAX:

mixed call_user_func ( callback $function [, mixed $parameter [, mixed $... ]] )

EXAMPLE:

function Box($width) {
   echo “Box Width:”.$width;
}

call_user_func('Box', array('width' => $w));

5. func_num_args:

With this function, you can easily get information about the number of arguments passed to the function.It returns the number of arguments passed into the current user-defined function.

SYNTAX:

int func_num_args ( void )

EXAMPLE:

function combined()
{
   $num_arg = func_num_args();
   echo "Number of arguments: $num_arg
";
}

combined('A,'B','C');

OUTPUT:

Number of arguments: 3

6. func_get_arg & func_get_args:

func_get_arg is a PHP function handling function will provide you information to get an array of all arguments passed to a user-defined function. func_get_args is to get the specified argument from a user-defined function’s argument list.

Function arguments are counting starts from zero

SYNTAX:

mixed func_get_arg ( int $arg_num )
array func_get_args ( void )

EXAMPLE:

function combined()
{
   $num_arg = func_num_args();
   if ($num_arg > 0) {
       echo "First argument is: " . func_get_arg(0) . "
n";
       $arg_list = func_get_args();
       for ($i = 0; $i < $num_arg; $i++) {
          echo "Argument $i is: " . $arg_list[$i] . "
";
      }
   }
}

combined('A,'B','C');

OUTPUT:

First argument is: A
Argument 0 is: A
Argument 1 is: B
Argument 2 is: C

7. get_defined_functions:

This function in useful to get an array of all defined functions.It returns a multidimensional array having a list of all defined functions.

SYNTAX:

array get_defined_functions ( void )

EXAMPLE:

function sample_test_func()
{
    return;
}
$array = get_defined_functions();

print_r($array);

OUTPUT:

Array
(
    [internal] => Array
        (
            [0] => zend_version
            [1] => func_num_args
            [2] => func_get_arg
            [3] => func_get_args
            [4] => strlen
            [5] => strcmp
            [6] => strncmp
            ...
            ...
        )

    [user] => Array
        (
            [0] => sample_test_func
        )

)

If you still have any questions or other tips to share, Do Share your opinion here in the comments!