Sorting a multidimensional array?

Question

I have an array that looks like this:

Array ( [0] => Array ( [filters] => Array ( [filter_1] => 1 
                                            [filter_2] => 1 
                                            [filter_3] => 1 
                                            [filter_4] => 1 
                                            [filter_5] => 1 
                                            [filter_6] => 1 ), 
                       [count]   => 2),

        [1] => Array ( [filters] => Array ( [filter_1] => 1 
                                            [filter_2] => 1 
                                            [filter_3] => 1 
                                            [filter_4] => 1 
                                            [filter_5] => 1 
                                            [filter_6] => 1 ), 
                       [count]   => 34)

        [2] => Array ( [filters] => Array ( [filter_1] => 1 
                                            [filter_2] => 1 
                                            [filter_3] => 1 
                                            [filter_4] => 1 
                                            [filter_5] => 1 
                                            [filter_6] => 1 ), 
                        [count]   => 7)

Is it possible to sort the main array keys by the [count] key in each, descending? So that they are in the following order: 1 -2 -0

Jack Murdoch · Accepted Answer · 2011-07-08 15:25:39Z

5

You'll need to use the uasort function. Try something like this:

function cmp($a, $b) {
    if ($a["count"] == $b["count"]) {
        return 0;
    }
    return ($a["count"] > $b["count"]) ? -1 : 1;
}

uasort($array, 'cmp');

answered Jul 8, 2011 at 15:25

Jack Murdoch

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rockerest · Accepted Answer · 2011-07-08 15:23:52Z

4

You definitely want the usort function. You can define how the sort function determines which is larger or smaller.

If it's alright that each sub-array (of "filters" and "count") gets re-indexed, this should work perfectly. By re-indexed, I mean the newly sorted array would start at 0, progress to 1, etc. This is almost always how you want it, unless your original array is associative.

For example:

usort($array, "byCount");

function byCount($a, $b)
{
    if( $a['count'] == $b['count'] )
    {
        return 0;
    }
    return ($a['count'] < $b['count']) ? -1 : 1;
}

answered Jul 8, 2011 at 15:23

rockerest

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5 Comments

Jack Murdoch Over a year ago

You could just use uasort to maintain key associations

rockerest Over a year ago

@Jack Murdoch, assuming @soren would ever want to access the array by index, uasort would be the exact opposite of what he would want. If $array[0] got sorted after $array[1], the resulting array would be $array( 1, 0 ) which is rarely useful, unless, like I mentioned in my answer, the array is associative.

Jack Murdoch Over a year ago

@rockerest Agreed, the only reason that I included this was because the OP mentioned that he wanted them to end up in the order "1 -2 -0".

rockerest Over a year ago

@Jack, that's a good point. I kind of glossed over that. I'm assuming that was just an example to show how he would want it to sort, but you bring up a good point.

Jack Murdoch Over a year ago

@rockerest He accepted yours, so obviously it was just for example ;)

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