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I can't seem to find anything of this, and was wondering if it's possible to store a function or function reference as a value for an array element (e.g. array("someFunc"=>&x(), "anotherFunc"=>$this->anotherFunc())). Thanks!

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4 Answers

up vote 5 down vote accepted

You can "reference" any function. A function reference is not a reference in the sense of "address in memory" or something. It's merely the name of the function.

<?php

$functions = array(
  'regular' => 'strlen',
  'class_function' => array('ClassName', 'functionName'),
  'object_method' => array($object, 'methodName'),
  'closure' => function($foo) {
    return $foo;
  },
);

// while this works
$functions['regular']();
// this doesn't
$functions['class_function']();

// to make this work across the board, you'll need either
call_user_func($functions['object_method'], $arg1, $arg2, $arg3);
// or
call_user_func_array($functions['object_method'], array($arg1, $arg2, $arg3));
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Okay, thanks! So ultimately, I suppose I'm looking for a means for creating a pointer. I don't want to duplicate a function, but merely want a pointer to it such that I can modify and read the value to which the pointer refers. – user784446 Feb 25 '12 at 13:00
Damn, just realized that call_user_func was an actual member of PHP's function-method library! Thanks! – user784446 May 19 '12 at 7:53
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up vote 1 down vote

check out PHP's call_user_func. consider the below example.

consider two functions

function a($param)
{
    return $param;
}

function b($param)
{
    return $param;
}


$array = array('a' => 'first function param', 'b' => 'second function param');

now if you want to execute all the function in a sequence you can do it with a loop.

foreach($array as $functionName => $param) {
    call_user_func($functioName, $param);
}

plus array can hold any data type, be it function call, nested arrays, object, string, integer etc. etc.

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up vote 0 down vote

Yes, you can:

$array = array(
    'func' => function($var) { return $var * 2; },
);
var_dump($array['func'](2));

This does, of course, require PHP anonymous function support, which arrived with PHP version 5.3.0. This is going to leave you with quite unreadable code though.

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That doesn't work for me, it returns UNEXPECTED T_FUNCTION error. – user784446 Feb 25 '12 at 13:05
What version of PHP are you using? It runs fine on my laptop, which is running PHP 5.3.6. If you are using 5.2 then this will definitely not work as mentioned in my answer above. – Treffynnon Feb 25 '12 at 13:06
Ah, okay. That's probably why. I'm using PHPDesigner2008, so it's error notification library is probably outdated. – user784446 Feb 25 '12 at 13:08
Yeah that is why I couldn't post a link to a work example on codepad.org. It must be running an older version of PHP. – Treffynnon Feb 25 '12 at 13:11
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up vote 0 down vote

PHP supports the concept of variable functions, so you can do something like this:

function foo() { echo "bar"; }
$array = array('fun' => 'foo');
$array['fun']();

Yout can check more examples in manual.

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Thanks, was thinking of doing that as a solution. But the docs also states that an element's value can be of any type, so why can't functions be used? I can use "element"=>object(), but don't know of what can be done with this. – user784446 Feb 25 '12 at 12:09
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