Anonymous Function return value

Question

Update: Starting with PHP7, it is now possible to use anonymous function dereferencing using the syntax:

$array[] = [
    'new' => (function()
    {
        ...
        return mt_rand();
    })(),

    'or' => getClosure()()
]

Original post: I've recently experimenting with some things, and wondered if there was any way to use the return value of an anonymous function

Lets say I had a for-loop that made an array that each value of the array had to have a database call, something I would like to do is:

for($i = 0; $i != 10; $i++)
{
    $array[] = [
        'new' => function(){
            // some proccesing here maybe
            // lets use mt_rand for this example.
            return mt_rand();
        },

        'old' => function(){
            return mt_rand();
        }
    ];
}

or maybe

echo function(){
     // again, we'll just use mt_rand
     return mt_rand();
};

These both return a closure class. Is there anyway to actually pass the return value of them back to the array or echo, for the examples above?

Update: I've established this isn't possible so, feature request can be found here: http://bugs.php.net/bug.php?id=64608

Do you really need an anonymous function? Sounds like you need a regular one and just call it inside the loop — kero
– kero, Commented Apr 7, 2013 at 22:40
Depends on what php version you have... I believe php 5.4 might be able to do this, but servers running older packages (i.e. Debian Squeeze I know runs php 5.3) won't. — Julian H. Lam
– Julian H. Lam, Commented Apr 7, 2013 at 22:41
@JulianH.Lam Anonymous functions are available since PHP 5.3 — Halim Qarroum
– Halim Qarroum, Commented Apr 7, 2013 at 22:43
I've established this isn't possible so, feature request can be found here: bugs.php.net/bug.php?id=64608 — Jordan Doyle
– Jordan Doyle, Commented Apr 7, 2013 at 23:10

deceze · Accepted Answer · 2013-04-07 23:39:09Z

25

Simplest workaround to date:

echo call_user_func(function () { return 'foo'; });

answered Apr 7, 2013 at 23:39

deceze♦

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1 Comment

Jordan Doyle Over a year ago

anonymous function dereferencing is now available in PHP7!

Community · Accepted Answer · 2017-05-23 11:46:25Z

2

Try assigning the anonymous function to a variable.

$myFunc = function() {
  return 'Test';
}

echo $myFunc(); // Outputs Test

The value of the function itself is not the return value. The return value is the value returned by the function when the function is called.

Edit:

As suggested by deceze, you can use call_user_func(). Another way to achieve what you want is to make use of php's eval(), which is by no means a good coding practice.

$array[] = array(
  'new' => call_user_func(function() {
     // some proccesing here maybe
     // lets use mt_rand for this example.
     return mt_rand();
  }),
  'old' => call_user_func(function() {
    return mt_rand();
  }),
);

eval()

echo eval('$x = function() {
  // some proccesing here maybe
  // lets use mt_rand for this example.
  return mt_rand();
}; return $x();');

edited May 23, 2017 at 11:46

CommunityBot

11 silver badge

answered Apr 7, 2013 at 22:41

Aiias

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4 Comments

user142162 Over a year ago

I believe OP is looking for the value to be returned when accessing $myFunc, not $myFunc().

Sam Over a year ago

@TimCooper No, you need the function calling, see here codepad.viper-7.com/3nnjGW

user142162 Over a year ago

@Sam: Yes, I am aware you have to evaluate the function to get the return value, but I believe this is a question on where you do the evaluating. I think OP wants the anonymous function to be evaluated when it's defined.

deceze Over a year ago

eval is about the worst solution to this.

David Farrell · Accepted Answer · 2014-02-03 21:10:06Z

1

The closure appears to have to be assigned before it can be de-referenced - Try this below code:

for($i = 0; $i != 10; $i++)
{
    $array[] = [
    'new' => call_user_func(function(){
        // some proccesing here maybe
        // lets use mt_rand for this example.
        return mt_rand();
    }),

    'old' => call_user_func(function(){
        return mt_rand();
    })
    ];
}

[edit] - Modified to use call_user_func() instead of custom function - doh!

edited Feb 3, 2014 at 21:10

answered Apr 7, 2013 at 23:36

David Farrell

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Comments

Sam · Accepted Answer · 2013-04-07 22:44:46Z

0

You must assign the function to a var, look here

This work

    for($i = 0; $i != 10; $i++)
 {
$array[] = [
    'new' => function(){
        // some proccesing here maybe
        // lets use mt_rand for this example.
        return mt_rand();
    },

    'old' => function(){
        return mt_rand();
    }
];
}
echo $array[5]['new']();

or

$function = function(){
 // again, we'll just use mt_rand
 return mt_rand();
};

echo $function();

answered Apr 7, 2013 at 22:44

Sam

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2 Comments

Jordan Doyle Over a year ago

In my case I need the return straight off the bat, Running $a = function(){ return mt_rand(); }(); doesn't work.

Sam Over a year ago

Because that is an assignament, you can do $a(), what's the problem?

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