Sorting an array using usort and a dynamic generated function

Question

I am using php function usort to sort an array. The custom php function must be generated because its dynamic

$intCompareField = 2;
$functSort = function($a, $b) {
  return ($a[$intCompareField] > $a[$intCompareField])?1:-1;
}

usort($arrayToSort, $functSort);

The $intCompareField in the compare function is null, my guessing is because the $intCompareField was declared outside of the function. Setting global $intCompareField does not seem to work.

Ps: I am using $intCompareField because the array to sort is multidimensional and i want to be able what key in the array to sort.

Are you sure you want to only ever return 1 or -1, it is generally desired to return 0 for "equal" values. — salathe
– salathe, Commented Jan 25, 2012 at 9:12
I know that but i want to keep the function short. Thanks tough for the comment — keepwalking
– keepwalking, Commented Jan 27, 2012 at 10:21
So, you prefer short and broken over short —though not as short as before— and working? Good luck with that! — salathe
– salathe, Commented Jan 27, 2012 at 13:25

Community · Accepted Answer · 2017-05-23 11:51:38Z

4

While Dor Shemer's answer would suffice, I find it often better to have a function which generates the required comparison function.

$functSort = function ($field) {
    return function($a, $b) use ($field) {
        // Do your comparison here
    };
};

$intCompareField = 2;
usort($arrayToSort, $functSort($intCompareField));

You could make the function in $functSort be a named function (e.g. sort_by_field_factory() or some other appropriate name), there's no requirement for it to be an anonymous function.

edited May 23, 2017 at 11:51

CommunityBot

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answered Jan 25, 2012 at 9:09

salathe

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Comments

dorsh · Accepted Answer · 2012-01-25 09:03:39Z

3

Try adding use, which passes variables from the outer scope to anonymous functions

function($a, $b) use ($intCompareField) {
     return ($a[$intCompareField] > $a[$intCompareField])?1:-1;
}

answered Jan 25, 2012 at 9:03

dorsh

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