PHP Unconference Europe 2015

func_get_arg

(PHP 4, PHP 5)

func_get_argRetourne un élément de la liste des arguments

Description

mixed func_get_arg ( int $arg_num )

Récupère un élément de la liste des arguments d'une fonction utilisateur.

func_get_arg() peut être utilisé conjointement à func_num_args() et func_get_args() pour permettre aux fonctions utilisateurs d'accepter un nombre variable d'arguments.

Liste de paramètres

arg_num

La position de l'argument. Les arguments de la fonction sont comptés en commençant à partir de 0.

Valeurs de retour

Retourne l'argument spécifié, ou FALSE si une erreur survient.

Historique

Version Description
5.3.0 Cette fonction peut maintenant être utilisée dans des listes de paramètres.
5.3.0 Si cette fonction est appelée depuis le scope le plus éloigné d'un fichier qui a été inclus via include ou require depuis l'intérieur d'une fonction du fichier appelant, elle génère une alerte et retourne FALSE.

Erreurs / Exceptions

Générera une alerte si elle est appelée hors d'une fonction utilisateur, ou si arg_num est plus grand que le nombre d'arguments passés.

Exemples

Exemple #1 Exemple avec func_get_arg()

<?php
function foo()
{
     
$numargs func_num_args();
     echo 
"Nombre d'arguments : $numargs<br />\n";
     if (
$numargs >= 2) {
         echo 
"Le second argument est : " func_get_arg(1) . "<br />\n";
     }
}

foo (123);
?>

Exemple #2 Exemple avec func_get_arg() avant et après PHP 5.3

test.php
<?php
function foo() {
    include 
'./fga.inc';
}

foo('First arg''Second arg');
?>

fga.inc
<?php

$arg 
func_get_arg(1);
var_export($arg);

?>

Affiche, avant PHP 5.3 :

'Second arg'

Affiche, en PHP 5.3 et suivants :

Warning: func_get_arg():  Called from the global scope - no function
context in /home/torben/Desktop/code/ml/fga.inc on line 3
false

Exemple #3 Exemple func_get_arg() avec des arguments par référence et par valeur

<?php
function byVal($arg) {
    echo 
'Tel que passé     : 'var_export(func_get_arg(0)), PHP_EOL;
    
$arg 'baz';
    echo 
'Après changement  : 'var_export(func_get_arg(0)), PHP_EOL;
}

function 
byRef(&$arg) {
    echo 
'Tel que passé     : 'var_export(func_get_arg(0)), PHP_EOL;
    
$arg 'baz';
    echo 
'Après changement  : 'var_export(func_get_arg(0)), PHP_EOL;
}

$arg 'bar';
byVal($arg);
byRef($arg);
?>

L'exemple ci-dessus va afficher :


Tel que passé : 'bar'
Après changement : 'bar'
Tel que passé : 'bar'
Après changement : 'baz'

Notes

Note:

Parce que cette fonction dépend de la portée courante pour déterminer les détails des paramètres, ils ne peuvent être utilisés en tant que paramètre d'une fonction dans les versions antérieures à 5.3.0. Si vous devez passer cette valeur, assignez les résultats à une variable et utilisez-la.

Note:

Si les arguments sont passés par référence, toutes leurs modifications seront reflétées dans les valeurs retournées par cette fonction.

Note: Cette fonction retourne uniquement une copie des arguments passés, et ne compte pas en tant qu'arguments par défaut (non passés).

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User Contributed Notes 8 notes

up
0
beta3designs [at] gmail [dot] com
5 years ago
This functions seems so powerful... just when i saw it i thought about writing a fast average of n numbers function so here it is, it is very simple... example usage included.

<?php

//Calculate the average of the numbers given

function avg(){
   
$sum = 0;
    for(
$i = 0; $i < func_num_args(); $i++){
       
$sum += func_get_arg($i);
    }
   
$avg = $sum / func_num_args();
    return
$avg;
}

echo
sprintf("%.2f",avg(2,1,2,1,3,4,5,1,3,6));
?>
up
0
dvogel at ssc dot wisc dot edu
10 years ago
I've always wants a deferment or cascade operator so that I could use this expression:

  $a = $b ## $c ## $d;

and everything to the right of the assignment operator would evaluate to the left-most value that is not null. It is essentially a collapsed version of this:

<?php
 
if ($b) {
   
$a=$b;
  } else {
    if(
$c) {
     
$a=$c;
    } else {
      if (
$d) {
       
$a = $d;
      } else {
       
$a = null;
      }
    }
  }
?>
In leiu of this, I'm trying to make a function that takes a variable number of arguments and returns the first that is not null. I wan't to use this on some large-ish arrays, so I'd like to pass these by reference. However, call-time reference passing is disabled (and should be, imo) in newer versions of PHP. I'd like suggestions on how to pass both references and values to this function.

The only solution I can think of is setting variables to the reference of the array first. e.g.

$a = array( ... );
$b = 0;
$c = &a;
first_not_null($a, $b);

Does anyone know a better solution?
up
0
harald at triptop dot org
10 years ago
func_get_arg is useful, if you know the exact order of the arguments, or if the order doesn't matter. i use this function (or func_get_args) for example to create own sprintf wrappers.

if you want to pass a variable number of arguments to a function it's in my opinion better, to submit it as a key/value array e.g.:

<?php
functioncall
(array("param1" => "...",...));
?>

and 'extract' the array inside the function. you don't need to do tricks like type-checking for parameter-recognition, in this case.
up
0
anders at ingemann dot fakestuff dot de
10 years ago
I actually think that there is need for such "do absolutely everything" functions. I use them mostly as tools for rapid prototyping.
And there is a method with which you may be able to pass several strings to a function: ereg();
Another use for such functions is to create little code snippets for other people out there. They won't have to edit the function any longer if they do not use a parameter. They just don't name it when calling the function.
This results in allrounder functions that are very robust in their use.Normally you just have a little code snippet (e.g. ip-blocking snippets). Through this type of programming you have whole functions.
up
0
Anonymous
10 years ago
very clever unless you need to specify at least two parameters of the same type - which is which? Obviously, you may decide on some defaults, but then the whole thing gets ugly. What if you need a string ONLY if a boolean was also supplied? The type-checking becomes the main focus of your function, shit. For the sake of clean code you should specify a clean interface to your functions, and decide on what and where is passed as an argument. Yes, you can always code a do_absolutely_everything() function, but is there any sense?
up
0
mightye (at) mightye (dot) org
10 years ago
func_get_arg() returns a *copy* of the argument, to my knowledge there is no way to retrieve references to a variable number of arguments.

I have a module system in my game at http://lotgd.net where I'd like to be able to pass a variable number of arguments to functions in a module, and pass them by reference if the module asks for it by reference, but you can't accept optional parameters as references, nor can you retrieve the reference on a variable number of arguments.  Looks like my modules will have to do with out the ability to accept parameters to their functions by reference.
up
-1
wintermute
7 years ago
Bishop: Your ternary example is flawed:

<?php
// using ternary operators
function pick($a,$b) { return (isset($a) ? $a : $b); }
$a = (pick($b,$c) ? pick($c,$d) : null);
?>

If $b is not null, it will evaluate pick($c, $d) and return $c if that is not null. If $b and $c are both null, it will not evaluate pick($c, $d) and will return null regardless of the value of $d. I'm not sure how you'd save this.

Another option would be to use an array:
<?PHP
function pick($array)
{
  foreach (
$array as $element)
  {
    if (
$element != null)
    {
      return(
$element)
    }
  }
  return(
null);
}

$a = pick(array($b, $c, $d, $e))
?>

I don't know that there's any real difference between this and the variable-argument form, but some people might prefer it, so it's worth noting.
up
-1
mw atto lanfear dotto com
9 years ago
func_get_arg() does not appear to be allowed to be used as a function argument itself within class constructors in PHP 5.0.2 (wonk-ay!!!):

<?php

class ABC
{
    function
__construct()
    {
        foreach (
func_get_args() as $name => $value)
        {
    echo <<<EOT
    <br/>
   
$name : $value <br/>
    <br/>

EOT;
        }
    }
}

class
DEF extends ABC
{
    function
__construct()
    {
       
parent::__construct(func_get_arg(0),
                                   
func_get_arg(1),
                                   
func_get_arg(2));
    }
}

$def = new DEF(123123, "asdfasdf", "blahblahblah");

?>

The above script generates:

Fatal error: func_get_arg(): Can't be used as a function parameter in c:\Inetpub\wwwroot\phpwasrc\chapter10\xxx.php on line 23

There are, however, no problems when passing these as parameters to regular functions.
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