In fact it is simple ISO8601 date. Split string with regexp like (\d+)
to minutes and seconds. Then get integer part of division of minutes by 60 to get hours. Get remainder of that division to get minutes.
here is an example that should work though i didn't tested it
preg_match_all('/(\d+)/',$youtube_time,$parts);
$hours = floor($parts[0][0]/60);
$minutes = $parts[0][0]%60;
$seconds = $parts[0][1];