如何根据两个键值对数组键进行排序？

Question

Let's say I need to run a for loop through an array where I need to check against to key value. I would like to print the array element that doesn't match BEFORE the element that doesn't match.

So using the array from below (extra values added for clarity), I would like it to print as follows. It needs to match the current_tag and last_tag values. If they don't match, that key needs to be printed prior to the others.

Desired results

TEST2

TEST1 
TEST3 
TEST4 

Array

array(2) {
    [0]=>
    array(3) {
        ["name"]=>
            string(3) "TEST1"
        ["current_tag"]=>
            string(13) "20121129_TEST1"
        ["last_tag"]=>
            string(13) "20121129_TEST1"
    }
    [1]=>
    array(3) {
        ["name"]=>
            string(3) "TEST2"
        ["current_tag"]=>
            string(13) "20121205_TEST2"
        ["last_tag"]=>
            string(13) "20121129_TEST2"
    }
    ...
    ...
    ...
    ...
}

Answer 1

I would usort the array with a custom callback to sort the array. After sorting you can just print every name key.

usort($array, function($a, $b) {
    $match_a = $a['current_tag'] == $a['last_tag'];
    $match_b = $b['current_tag'] == $b['last_tag'];

    if ($match_a && $match_b) {
        return 0;
    } elseif ($match_a && !$match_b) {
        return 1;
    } elseif (!$match_a && $match_b) {
        return -1;
    }
});

array_walk($array, function($item) {
    echo $item['name'];
});

If it is ordered in the wrong order just switch the 1 and -1 return values.