Sort array of sizes relative to amount of X's (XXS, S, M, L, XL, etc)

sizeSort.php

<?php

$sizes = array("XS", "L", "M", "S", "XXS", "XXL", "XXS", "M", "XXXXXL", "XL");

// Function doesn't handle (X+)M, because that would make no sense at all.
function sizeSort($cmp1, $cmp2)
{
    $sort = array("S", "M", "L");
    if (preg_match("/(^[X]*)([SML])$/is", $cmp1, $parts_1) && preg_match("/(^[X]*)([SML])$/is", $cmp2, $parts_2)) {

        $weight_1 = array_search($parts_1[2], $sort);
        $weight_2 = array_search($parts_2[2], $sort);
        if ($weight_1 !== $weight_2) {
            return ($weight_1 < $weight_2 ? -1 : 1);
        }

        $sub_weight_1 = strlen($parts_1[1]);
        $sub_weight_2 = strlen($parts_2[1]);
        if ($sub_weight_1 !== $sub_weight_2) {
            if ($weight_1 > 1) {
                //L so more X is higher
                return ($sub_weight_1 > $sub_weight_2 ? 1 : -1);
            } elseif ($weight_1 < 1) {
                //S so more X is lower
                return ($sub_weight_1 > $sub_weight_2 ? -1 : 1);
            }
        }
    }

    return 0; // same input
}

usort($sizes, "sizeSort");

//output : XXS, XXS, XS, S, M, M, L, XL, XXL, XXXXXL