รบกวนชี้แนะคำสั่ง elseif ของผมหน่อยคับ งงคับ.คำสั่ง elseif อันสุดท้าย ไม่ทำงานคับ ช่วยผมหน่อยคับ

$hostname = "localhost"; //?
			$user = "root"; //?
			$password = "root"; //??
			$dbname = "car"; //??
			$tblname = "data"; //??
			 
        if ($_POST['drive_name'] !='ทั้งหมด' and $_POST['department'] !='ทั้งหมด' and $_POST['car_number'] !='ทั้งหมด'  )
              { $sql ="SELECT * FROM data
                       where drive_name='$drive_name' and department='$department' and car_number='$car_number' and start_mile!='0' ";}
                    
                 
					 elseif ($_POST['drive_name'] !='ทั้งหมด' and $_POST['department'] ='ทั้งหมด' and $_POST['car_number'] ='ทั้งหมด' )
                     { $sql ="SELECT * FROM data
                     where drive_name='$drive_name' and start_mile!='0'";}
					
					elseif ($_POST['drive_name'] ='ทั้งหมด' and $_POST['department'] !='ทั้งหมด' and $_POST['car_number'] ='ทั้งหมด' )
                     { $sql ="SELECT * FROM data
                     where department='$department' and start_mile!='0'";}
					
					elseif ($_POST['drive_name'] ='ทั้งหมด' and $_POST['department'] ='ทั้งหมด' and $_POST['car_number'] !='ทั้งหมด' )
                     { $sql ="SELECT * FROM data
                     where car_number='$car_number' and start_mile!='0'";}
					 
					 elseif ($_POST['drive_name'] !='ทั้งหมด' and $_POST['department'] !='ทั้งหมด' and $_POST['car_number'] ='ทั้งหมด' )
                     { $sql ="SELECT * FROM data
                     where department='$department' and drive_name='$drive_name' and start_mile!='0'";}
					
             else
                { $sql ="SELECT * FROM data where year_round='$year_round'and start_mile!='0'
                       ";}

            elseif ($_POST['drive_name'] !='ทั้งหมด' and $_POST['department'] !='ทั้งหมด' and $_POST['car_number'] ='ทั้งหมด' )
                     { $sql ="SELECT * FROM data
                     where department='$department' and drive_name='$drive_name' and start_mile!='0'";}