Sort Multidimensional arrays by sub array key value

Question

There are similar questions and answers posted for this, but none of them quite match the structure of my array, so apologies if I missed something. This is an array generated by the WordPress wpdb class:

Array ( 
[0] => Array ( [meta_id] => 37850 [post_id] => 5548 [meta_key] => Item # [meta_value] => 66002 ) 
[1] => Array ( [meta_id] => 37851 [post_id] => 5548 [meta_key] => Hex Size [meta_value] => .051" ) 
[2] => Array ( [meta_id] => 37852 [post_id] => 5548 [meta_key] => Across Flats [meta_value] => 0.051 ) 
[3] => Array ( [meta_id] => 37853 [post_id] => 5548 [meta_key] => Type [meta_value] => Hexagonal ) 
[4] => Array ( [meta_id] => 37854 [post_id] => 5548 [meta_key] => Shank [meta_value] => .315" ) ) 

Array ( 
[0] => Array ( [meta_id] => 37910 [post_id] => 5553 [meta_key] => Item # [meta_value] => 66008 ) 
[1] => Array ( [meta_id] => 37911 [post_id] => 5553 [meta_key] => Hex Size [meta_value] => 1/8" ) 
[2] => Array ( [meta_id] => 37912 [post_id] => 5553 [meta_key] => Across Flats [meta_value] => 0.127 ) 
[3] => Array ( [meta_id] => 37913 [post_id] => 5553 [meta_key] => Type [meta_value] => Hexagonal ) 
[4] => Array ( [meta_id] => 37914 [post_id] => 5553 [meta_key] => Shank [meta_value] => .315" ) ) 

Array ( 
[0] => Array ( [meta_id] => 37862 [post_id] => 5549 [meta_key] => Item # [meta_value] => 66004 ) 
[1] => Array ( [meta_id] => 37863 [post_id] => 5549 [meta_key] => Hex Size [meta_value] => 1/16" ) 
[2] => Array ( [meta_id] => 37864 [post_id] => 5549 [meta_key] => Across Flats [meta_value] => 0.063 ) 
[3] => Array ( [meta_id] => 37865 [post_id] => 5549 [meta_key] => Type [meta_value] => Hexagonal ) 
[4] => Array ( [meta_id] => 37866 [post_id] => 5549 [meta_key] => Shank [meta_value] => .315" ) ) 

Array ( 
[0] => Array ( [meta_id] => 37886 [post_id] => 5551 [meta_key] => Item # [meta_value] => 66006 ) 
[1] => Array ( [meta_id] => 37887 [post_id] => 5551 [meta_key] => Hex Size [meta_value] => 3/32" ) 
[2] => Array ( [meta_id] => 37888 [post_id] => 5551 [meta_key] => Across Flats [meta_value] => 0.095 ) 
[3] => Array ( [meta_id] => 37889 [post_id] => 5551 [meta_key] => Type [meta_value] => Hexagonal ) 
[4] => Array ( [meta_id] => 37890 [post_id] => 5551 [meta_key] => Shank [meta_value] => .315" ) ) 

I need to list them by order of Array[meta_value]. Then I use the array to generate a table of products in that order. I have been working with the following function, but it produces a result that doesn't make any sense:

function subval_sort($a,$subkey) {
    foreach($a as $k=>$v) {
        $b[$k] = strtolower($v[$subkey]);
    }
    asort($b);
    foreach($b as $key=>$val) {
        $c[] = $a[$key];
    }
    return $c;
}

Solution

Use usort(), example:

$items = [
    ['id' => 3, 'item' => 'pc'],
    ['id' => 1, 'item' => 'mouse'],
    ['id' => 2, 'item' => 'kb'],
];

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

usort($items, 'compare_id');

var_dump($items);    

or using anonymous function

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

Comments

[Laci]

This should be the accepted answer. Got it work in a blink of the eye!