How can I write out PHP INSERT TO Command?

$sql = "INSERT INTO class_schedule
   (date, start_id, end_id, classroom_id, type_id, name_id)
    VALUES (
      '". $_REQUEST['date'] ."',
       '". $_REQUEST['start'] ."',
       '". $_REQUEST['end'] ."',
        ". $_REQUEST['classroom'] .",
         ". $_REQUEST['type'] .",
         ". $_REQUEST['name'] ."  
     )";

Is this the way to write it all out? I don't know if the quotes are written out correctly.