How can I optimize my array_join (simulates a LEFT JOIN) function?

Question

I wrote the following code to take arrays in PHP and \"join\" them together the way that a LEFT JOIN would in MySQL. For my sake I wrote the function using foreach and passed th

Answer 1

Better?

function array_join($original, $merge, $on) {
    if (!is_array($on)) $on = array($on);
    foreach ($merge as $remove => $right) {
        foreach ($original as $index => $left) {
            foreach ($on as $from_key => $to_key) {
                if (!isset($original[$index][$from_key])
                || !isset($right[$to_key])
                || $original[$index][$from_key] != $right[$to_key])
                    continue 2;
            }
            $original[$index] = array_merge($left, $right);
            unset($merge[$remove]);
        }
    }
    return array_merge($original, $merge);
}