PHP Australia Conference 2015

func_get_arg

(PHP 4, PHP 5)

func_get_argLiefert ein bestimmtes Funktionsargument

Beschreibung

mixed func_get_arg ( int $arg_num )

Liefert das mit arg_num angegebene Argument aus der Liste der Argumente einer benutzerdefinierten Funktion.

Diese Funktion kann zusammen mit func_get_args() und func_num_args() genutzt werden um benutzerdefinierte Funktionen mit einer variablen Anzahl von Argumenten zu implementieren.

Parameter-Liste

arg_num

Der Offset des Arguments. Funktionsargumente werden mit 0 beginnend gezählt.

Rückgabewerte

Liefert das gewünschte Argument oder FALSE bei Fehlern.

Changelog

Version Beschreibung
5.3.0 Diese Funktion kann nun auch in Parameterlisten genutzt werden.

Fehler/Exceptions

Die Funktion generiert eine Warnung wenn sie außerhalb einer benutzerdefinierten Funktion aufgerufen wird oder wenn arg_num größer ist als die Anzahl der tatsächlich übergebenen Argumente.

Beispiele

Beispiel #1 func_get_arg() Beispiel

<?php
function foo()
{
     
$numargs func_num_args();
     echo 
"Anzahl der Funktionsargumente: $numargs<br />\n";
     if (
$numargs >= 2) {
         echo 
"Das zweite Argument ist: " func_get_arg(1) . "<br />\n";
     }
}

foo (123);
?>

Anmerkungen

Hinweis:

Da diese Funktion bei der Ermittlung der Parameterdetails von dem aktuellen Ausführungskontext abhängt, kann sie in PHP-Versionen vor 5.3.0 selbst nicht als Funktionsparameter genutzt werden. Wenn Sie ihre Ergebnisse tatsächlich weitergeben müssen, so müssen Sie diese zunächst einer Variablen zuweisen und dann diese Variable übergeben

Hinweis: Diese Funktion liefert eine Kopie des übergebenen Arguments. Sie hat nur Zugriff auf tatsächlich übergebene Argumente, Vorgabewerte von Parametern sind für sie nicht sichtbar.

Siehe auch

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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
9 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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