PHP nested functions use a variable of the outer one in the inner one

Question

I want to sort bidimensional associative arrays by a given key, using uasort.

I have tried

function sortBy(&$arr, $key) {
    $cmp = function($a, $b) {
        global $key;
        return $a[$key] < $b[$key] ? -1 :
               $a[$key] == $b[$key] ? 0 : 1;
    };
    return uasort($arr, $cmp);
}

But $key is undefined inside $cmp.

You can do function (args) use (variables). Another option is to get object oriented as I answered at this question. — crush
– crush, Commented Feb 4, 2014 at 21:23

oleksii.svarychevskyi · Accepted Answer · 2014-02-04 21:20:48Z

4

Try to use this

function sortBy(&$arr, $key) {
    $cmp = function($a, $b) use ($key) {
        return $a[$key] < $b[$key] ? -1 :
           $a[$key] == $b[$key] ? 0 : 1;
    };
    return uasort($arr, $cmp);
}

answered Feb 4, 2014 at 21:20

oleksii.svarychevskyi

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Comments

Michal Artazov · Accepted Answer · 2014-02-04 21:26:47Z

2

This should solve the problem

function sortBy(&$arr, $key) {
    $cmp = function($a, $b) use($key) {
        global $key;
        return $a[$key] < $b[$key] ? -1 :
               $a[$key] == $b[$key] ? 0 : 1;
    };
    return uasort($arr, $cmp);
}

Notice that I added use($key) into the declaration of the nested function. You can find out more here http://www.php.net/manual/en/functions.anonymous.php

answered Feb 4, 2014 at 21:26

Michal Artazov

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