$to = \Carbon\Carbon::createFromFormat('Y-m-d H:s:i', '2015-5-6 3:30:34');
$from = \Carbon\Carbon::createFromFormat('Y-m-d H:s:i', '2015-5-6 3:30:54');


$diff_in_minutes = $to->diffInMinutes($from);
print_r($diff_in_minutes); // Output: 20