func_get

Description

array func_get_args ( void )

Returns an array in which each element is a copy of the corresponding member of the current user-defined function's argument list. func_get_args() will generate a warning if called from outside of a function definition. This function cannot be used directly as a function parameter. Instead, its result may be assigned to a variable, which can then be passed to the function.

注: This function returns a copy of the passed arguments only, and does not account for default (non-passed) arguments.

注: 因为本函数依赖于当前域来决定参数细节，因此不能用作函数参数。如果必须要传递这个值，将结果赋给一个变量，然后传递该变量。


<?php
function foo() 
{
    $numargs = func_num_args();
    echo "Number of arguments: $numargs<br />\n";
    if ($numargs >= 2) {
        echo "Second argument is: " . func_get_arg(1) . "<br />\n";
    }
    $arg_list = func_get_args();
    for ($i = 0; $i < $numargs; $i++) {
        echo "Argument $i is: " . $arg_list[$i] . "<br />\n";
    }
} 

foo(1, 2, 3);
?>

func_get_args() may be used in conjunction with func_num_args() and func_get_arg() to allow user-defined functions to accept variable-length argument lists.

add a note User Contributed Notes

01-Nov-2006 02:26


Same idea as below, but this:



       foreach( $args as $k => $v ){

           switch($k){

               case 'a':

                   $this->a= $v; break;

               case 'b':

                   $this->b= $v; break;

               case 'c':

                   $this->c= $v; break;

             }

       }



can be shortened to this (as long as all public variables have default values set in their declarations):



       foreach( $args as $k=>$v) 

            if(isset($this->$k)) $this->$k = $v;

kidekat
01-Oct-2006 09:02


To pass named arguments in a Perl fashion through class constructors, I use this:



<?php

class Test{



    // set class defaults for values not assigned by constructor

    public $a = 0;

    public $b = 'string';

    public $c = array();



    public function __construct( $args = array() ) {



        // parse tagged arguments in Perl fashion

        foreach( $args as $k => $v ){

            switch($k){

                case 'a':

                    $this->a= $v; break;

                case 'b':

                    $this->b= $v; break;

                case 'c':

                    $this->c= $v; break;

             }

        }

    }



}



$t = new Test(  array( 'b'=>'new value', 'c'=>array(1,'test') ) );

?>



This allows $a to keep its default of 0, while $b gets reassigned to 'new value' and $c becomes the array(1,'test'). The catch is that you add O(n^2) "big-O notation" to the begging of every class constructor which becomes expensive on "larger" classes. While arguments defaults like the following have only O(n) "constant" amount of work.



<?php

    public funciton __construct( $a=0, $b='string', $c=array()){ ... }

?>

bew
31-Mar-2006 11:55


A more concise way of expressing my idea from the previous post (I'd forgotten about array_slice()):



<?php

function func_get_default_args($a) {

    $args = array_slice(func_get_args(), 1);

    return array_merge($args, array_slice($a, sizeof($args)));

}



function foo($a = 1, $b = 2, $c = 3) {

    print_r(func_get_default_args(func_get_args(), $a, $b, $c));

}



// prints: Array ( [0] => a [1] => b [2] => 3 )

foo('a', 'b');

?>

Nathan Ostgard
07-Dec-2005 02:14


If you're using PHP5, the variable number of argument functions all return the objects by reference - and not a copy of the object, as this leads you to believe.

robert at defore dot st
15-Feb-2005 04:47


# Another attempt at named args (perl-inspired):



# list_to_assoc('key', 'value', 'key', 'value', ...) =>

#     pairs[]

function list_to_assoc() {

    $list = func_get_args();

    $assoc = array();



    while ($list and count($list) > 1) {

        $assoc[array_shift($list)] = array_shift($list);

    }



    if ($list) { $assoc[] = $list[0]; }



    return $assoc;

}



# Usage:



function example($required) {

    $args = func_get_args(); array_shift($args); # drop 'required'

    $rest = list_to_assoc($args);

    echo "$required\n" . $rest['comment']; 

}



example("This is required...", 

        'comment', 'this is not.'); # this is like 'comment' => 'this is not'

T.M.
04-Nov-2004 11:24


Simple function to calculate average value using dynamic arguments:

<?php

function average(){

    return array_sum(func_get_args())/func_num_args();

}

print average(10, 15, 20, 25); // 17.5

?>

volte6 at drunkduck dot com
01-Oct-2004 05:54


For those who have a use for a C style enum() function:



//*******************************************

// void enum();

// enumerates constants for unique values guarenteed.

function enum()

{

  $i=0;

  $ARG_ARR = func_get_args();

  if (is_array($ARG_ARR))

  {

    foreach ($ARG_ARR as $CONSTANT)

    {

      define ($CONSTANT, ++$i);

    }

  }

}



// USAGE:

enum(ERR_USER_EXISTS, ERR_OLD_POST);



// etc. etc.

//*******************************************



this can be used for error codes etc.

I deliberately skipped the 0 (zero) define, which could be useful for error checking.

mark at manngo dot net
24-Mar-2003 03:13


You can also fake named arguments using eval:



function test()

{   foreach (func_get_args() as $k=>$arg) eval ("\$$arg;");

    echo "$a plus $b gives ".($a+$b);

}



test("a=3","b=4");

fbeyer at clickhand dot de dot noSpamPlease
20-Jan-2002 12:02


Another way of passing references with a dynamic number of arguments: (This example is limited to 10 arguments)



<?php

define('NULL_ARG', 'DUMMY_ARGUMENT');



function refArg($arg0 = NULL_ARG,

                $arg1 = NULL_ARG,

                $arg2 = NULL_ARG,

                $arg3 = NULL_ARG,

                $arg4 = NULL_ARG,

                $arg5 = NULL_ARG,

                $arg6 = NULL_ARG,

                $arg7 = NULL_ARG,

                $arg8 = NULL_ARG,

                $arg9 = NULL_ARG)

{

    for ($args=array(), $i=0; $i < 10; $i++) {

        $name = 'arg' . $i;

        if ($i < func_num_args()) {

            $args[$i] = &$$name;

        }

        unset($$name, $name);

    }



    $args[0] = 'Modified.';

}



$test = 'Not modified.<br>';

refArg(&$test);



echo $test; // Prints 'Modified'

?>

daveNO at ovumSPAMdesign dot com
18-Sep-2001 02:29


<?php


// How to simulate named parameters in PHP.


// By Dave Benjamin <dave@ovumdesign.com>





// Turns the array returned by func_get_args() into an array of name/value


// pairs that can be processed by extract().


function varargs($args) {


    $count = count($args);


    for ($i = 0; $i < $count; $i += 2) {


        $result[$args[$i]] = $args[$i + 1];


    }


    


    return $result;


}





// Example


function test(&$ref1, &$ref2) {


    // Default arguments go here.


    $foo = "oof";


    


    // Do some magic.


    extract(varargs(func_get_args()));





    echo nl2br("\n\$var1 = $var1");


    echo nl2br("\n\$var2 = $var2");


    echo nl2br("\n\$foo = $foo\n\n");


    


    // Modify some variables that were passed by reference.


    // Note that func_get_args() doesn't pass references, so they


    // need to be explicitly declared in the function definition.


    $ref1 = 42;


    $ref2 = 84;


}





$a = 5;


$b = 6;





echo nl2br("Before calling test(): \$a = $a\n");


echo nl2br("Before calling test(): \$b = $b\n");





// Try removing the 'foo, "bar"' from the following line.


test($a, $b, var1, "abc", var2, "def", foo, "bar");





echo nl2br("After calling test(): \$a = $a\n");


echo nl2br("After calling test(): \$b = $b\n");


?>

04-Jun-2001 10:44


You can pass a variable number of arguments to a function whilst keeping references intact by using an array. The disadvantage of course, is that the called function needs to be aware that it's arguments are in an array.


<?


// Prints "hello mutated world"


function mutator($args=null) {


$n=count($args);


while($i<$n) $args[$i++] = "mutated";


}


$a = "hello";


$b = "strange";


$c = "world";


mutator(array($a, &$b, $c));


echo "$a $b $c";


?>

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