func_num

Description

int func_num_args ( void )

Returns the number of arguments passed into the current user-defined function. func_num_args() will generate a warning if called from outside of a user-defined function. 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: 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\n";
} 

foo(1, 2, 3);    // Prints 'Number of arguments: 3'
?>

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

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neelam_ab2003 at yahoo dot co dot in
11-May-2006 03:40


Just adding a note to JARED's Note.



func_num_args() works if and only if called from within a function definition BECAUSE it calculates the number of arguments sent while function calling. That is why it gives 



'1' in helloWorld("HelloWorld!") and '2' in helloWorld("HelloWorld!", "HowdyWorld!") - There is nothing to do with DEFAULT args.



If you call the same function as helloWorld(); "No args passed"



It will give a warning for wrong function call ("Warning: Missing argument 1 for helloWorld()") and the result of func_num_args() will be '0'.

friz at godshell dot com
17-Mar-2006 03:24


This function comes in extremely handy in OO Classes.  My focus is currently PHP 4, but this technique probably works just as well in PHP 5.



Class foo {

   // constructor, other methods, etc



   function somedata($somedata = '') {

      if (func_num_args() > 0) {

         $this->somedata = $somedata;

      }



      return $this->somedata;

   }

}



This allows for a default value to be set, while not requiring the parameter.  (Yes, I'm aware that it only warns when you do, but I think this is a little cleaner)

jared at ws-db dot com
07-Sep-2005 12:46


Just a note for anyone wondering. This function doesn't include params that have a default value, unless you pass one in to overwrite the default param value. Not sure if that makes sense, so here's an example:



function helloWorld($ArgA, $ArgB="HelloWorld!") {

  return func_num_args();

}



// The following will return 1

$Returns1 = helloWorld("HelloWorld!");



// The following will return 2

$Returns2 = helloWorld("HelloWorld!", "HowdyWorld!");

andy at arakka dot co dot th
12-May-2005 10:16


func_num_args() can be used in conjunction with named arguments, also. For example:

function DebugShow( $label, $value ) {

  echo "# " . $label ;

  if ( func_num_args() > 1 ) echo " = " . $value ;

  echo "<br>";

}

ashley at dcs dot warwick dot ac dot uk
17-Apr-2002 07:40


If you want to pass the parameters on intact to another function, use func_get_args and call_user_func_array (careful - this one is only available in recent PHP versions).  For example:



/* Print an HTML tag.  This accepts a variable number of arguments:

   the first should be the name of the tag, followed by pairs of

   arguments that describe keys and values.  The values are printed

   with surrounding double quote characters.  */

function printTag() {

  $numArgs = func_num_args();

  if ($numArgs < 1) die("printTag given no arguments");

  

  echo "<" . func_get_arg(0);

  for ($i = 1; $i < $numArgs; $i+=2) {

    echo " " . func_get_arg($i);

    if ($i+1 < $numArgs)

      echo "=\"" . func_get_arg($i+1) . "\"";

  }

  echo ">";

  

}



/* Print an HTML tag with a newline on the end */

function printTagNL() {

  $args = func_get_args();

  call_user_func_array("printTag", $args);

  echo "\n";

}



printTagNL("input", "type", "hidden", "name", "SORTORDER", "value", $columnNo);

thalis at NOSPAMcs dot pitt dot edu
30-Mar-2002 04:05


The idea of func_get_args() is to construct functions of variable number of parameters like

function var_param_func(){

    if(func_num_args()==0){

        //do one thing

    }

    if(func_num_args()==1)

        //do another thing

        //get the args with func_get_args()

    }

}

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