PHP 5.4.36 Released

func_get_arg

(PHP 4, PHP 5)

func_get_argDevuelve un elemento de una lista de argumentos

Descripción

mixed func_get_arg ( int $arg_num )

Obtiene el argumento especificado de una lista de argumentos de una función definida por el usuario.

Esta función se puede usar junto con func_get_args() y func_num_args() para permitir a las funciones de usuario aceptar listas de argumentos de longitud variable.

Parámetros

arg_num

El índice del argumento. Los argumentos de las funciones se empiezana contar desde cero.

Valores devueltos

Devuelve el argumento especificado, o FALSE en caso de error.

Historial de cambios

Versión Descripción
5.3.0 Esta función ahora se puede usar en listas de parámetros.
5.3.0 Si esta función es llamada desde el ámbito último de un archivo que ha sido incluido mediante una llamada a include o require desde dentro de una función en el archivo de llamada, ahora genera una advertencia y devuelve FALSE.

Errores/Excepciones

Genera una advertencia si se llama desde fuera de una función definida por el usuario, o si arg_num es mayor que el número de argumentos pasados actualmente.

Ejemplos

Ejemplo #1 Ejemplo de func_get_arg()

<?php
function foo()
{
     
$númargs func_num_args();
     echo 
"Número de argumentos: $númargs<br />\n";
     if (
$númargs >= 2) {
         echo 
"El segundo argumento es: " func_get_arg(1) . "<br />\n";
     }
}

foo (123);
?>

Ejemplo #2 Ejemplo de func_get_arg() antes y después de PHP 5.3

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

foo('Primer argumento''Segundo argumento');
?>

fga.inc
<?php

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

?>

Salida anterior a PHP 5.3:

'Segundo argumento'

Salida en PHP 5.3 y posterior:

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

Ejemplo #3 func_get_arg() ejemplo de argumentos byref (pasa un objeto como referencia) y byval (pasa un objeto como valor)

<?php
function byVal($arg) {
    echo 
'Pasó como     : 'var_export(func_get_arg(0)), PHP_EOL;
    
$arg 'baz';
    echo 
'Tras el cambio: 'var_export(func_get_arg(0)), PHP_EOL;
}

function 
byRef(&$arg) {
    echo 
'Pasó como     : 'var_export(func_get_arg(0)), PHP_EOL;
    
$arg 'baz';
    echo 
'Tras el cambio: 'var_export(func_get_arg(0)), PHP_EOL;
}

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

El resultado del ejemplo sería:


Pasó como : 'bar'
Tras el cambio: 'bar'
Pasó como : 'bar'
Tras el cambio: 'baz'

Notas

Nota:

Como esta función depende del ámbito actual para determinar los detalles del parámetro, no puede ser usada como parámetro de función en versiones anteriores a 5.3.0. Si se require pasar el valor, los resultados deben ser asignados a una variable y esta variable debería pasarse como parámetro.

Nota:

Si los argumentos se pasan por su referencia, cualquier cambio en ellos será reflejado en los valores devueltos por esta función.

Nota: Esta función solamente devuelve una copia de los argumentos pasados, y no rinde cuentas de los argumentos predeterminados (no pasados).

add a note add a note

User Contributed Notes 8 notes

up
1
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
-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
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
mw atto lanfear dotto com
10 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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