Attendance system using PHP & MySQL

I am probably a bit late with my answer, but I have been playing around a bit too and came up with a solution that is largely done within MySql: my solution builds a dynamic SELECT statement that is executed at the end to provide me with the table, having columns spanning a predefined era:

SET @str='SELECT sid';
SELECT @str:=concat(@str,', MAX(CASE tid WHEN ',t_id,
                    ' THEN \'OK\' ELSE \'\' END) d',t_id) 
--                            start date          end date
FROM times WHERE dati BETWEEN '20170810.0000' and '20171022.2359';
SET @str=concat(@str,' FROM att GROUP BY sid');
PREPARE qu FROM @str;
EXECUTE qu;

What still needs to be done is the translation of date Ids in the column headings to proper dates and, likewise, the translation of student Ids into names or univ_roll numbers.

i have also taken the liberty of changing the table layout a little bit: the primary key in the timetable is now just an integer, the actual time is stored separately in another column, providing flexibility in case dates or times might change.

Here is a little rextester demo: http://rextester.com/LPFF99061 (the attendance table has only been filled for the first few dates).

I'm not sure if I should edit the question with these updates. But this is a partial solution that I did come out with. Would be glad if someone could help optimize this more.

So, I started with this piece of code.

SELECT timeid 
FROM timetable 
WHERE flag > ? 
  AND semester = ? 
  AND section = ? 
  AND timeid BETWEEN ? AND ?

From the above code I could get the dates where classes are taken. Next, I check if a student is present or absent on the dates mentioned as follows:

SELECT attended FROM attendancetable
    WHERE s_id = ?
    AND semester = ?
    AND timeid = ?

With this I was able to see if a student is absent or not. In php it look something like this:

//Getting the dates
$query = "SELECT timeid FROM timetable
        WHERE flag > ?
        AND semester = ?
        AND section = ?
        AND timeid BETWEEN ? AND ?";
$params = array(0, 1, 'A', '2017-01-01', '2017-06-30' );
$stmt = $db->prepare($query);
$stmt->execute($params);
$dates = $stmt->fetchall();

//checking if students is present or absent
$query = "SELECT attended FROM attendancetable
        WHERE s_id = ?
        AND semester = ?
        AND timeid = ?";

//Now I'm going to loop through the $dates
foreach($dates as $date){
    $params = array(1, 'A', $date['timeid']);
    $stmt = $db->prepare($query);
    $stmt->execute($params);
    $result = $stmt->fetchall();
    ($result) ? $present = 1 : $present = 0;
}

In the above way, I was able to compute if a student of a particular section is present/absent for a given class as per the timetable. Now, if I want for all the students in a section I could first query the student_info table and then compute the foreach loop for each individual student

SELECT class_roll FROM student_info
    WHERE logYear = ?
    AND section = ?
    AND deleted = ? 
    ORDER BY class_roll LIMIT ?, ?

Each student is then run through the foreach loop to check if they are absent or present. Finally, I could get this:

I tested the execution time locally for about 200 students it came to about 1.6 seconds when the number of classes is only 39. I do test from previous data also for a whole semester and the code exceed 30 seconds and max_execution_time error triggered. As of now, I set a 25 number of students limits per page.

UPDATE: The max_execution_time error seems to appear only on the first run, but later when I try to re-produce its not giving anymore error and the time taken to complete the task is below 2 seconds.