mktime() expects parameter 1 to be long string given

Question

how can i solve the warning in my page like mktime() expects parameter 1 to be long string given..

Here is my code

$next = date("Y-m-d H:i:s", mktime($t_parts[0],$t_parts[1],$t_parts[2],$d_parts[1],$d_parts[2],$d_parts[0]));