Sorts a multi-dimension array by datetime. Can be ASC or DESC.

sort_multidimension_array.php

/*
    Usage:
    usort($array, array($this, "date_compare"));
    
    To sort DESC use return $t2 - $t1
    To sort ASC use return $t1 - $t2
*/

public function date_compare($a, $b)
{
	$t1 = strtotime($a['datetime']);
	$t2 = strtotime($b['datetime']);
	return $t2 - $t1;
}