ต้องการเช็คเวลาเข้างานว่าสายหรือไม่ ถ้าสาย สายกี่นาที

<?php
	function TimeDiff($strTime1,$strTime2)
	 {
		return (strtotime($strTime2) - strtotime($strTime1))/  ( 60 * 60 ); // 1 Hour =  60*60
	 }
	 echo "สาย ".TimeDiff("00:00","19:00")." นาที"."<br>";
?>

select 
	tb1.em_id, tb1.stamp_check st, tb2.stamp_check en,
	((@st:=unix_timestamp(tb2.stamp_check)) - (@en:=unix_timestamp(tb1.stamp_check))) timework,
	(@late:=(@st - (@fixin:=unix_timestamp(concat(curdate(),' 08:00'))))) as latein,
	((@fixout:=unix_timestamp(concat(curdate(),' 17:00')))) as beforeout,
	(@en - @fixout - if(@late>0, @late, 0)) as overtime
from table as tb1, table as tb2
where tb1.em_id=tb2.em_id
and date(tb1.stamp_check) = date(tb2.stamp_check)
and tb1.action='in' and tb2.action='out'
and date(tb1.stamp_check)=curdate()