$qu3 = 'UPDATE logs SET out= '.date("Y-m-d H:i:s").' WHERE sl_no= '.$sno;
$r4 = mysql_query($qu3)or die(mysql_error());
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'out= 2017-07-11 23:04:52 WHERE sl_no= 73' at line 1