PHP function inside query wont return value - php

Question

So, I have a PHP Script that would insert an attendance of the student. First it should check if the attendance with the same student ID and date already exist. If not, it inserts the attendance. I want to insert in the attendance status whether the student is present or late based on my php function compareTime's return value. But the problem is, the function wont return anything. That's why in the attendance data the status column is blank.
function checkAttendance($conn, $stud_id) {
$check = mysqli_query($conn, "SELECT * FROM tbl_attendance WHERE student_id = '$stud_id' AND date = CURDATE()") or die (mysqli_error());
if(mysqli_num_rows($check) > 0) {
return true;
}
else {
return false;
}
}
function compareTime($time,$grade) {
$ctime = strtotime($time);
if($grade == "H1" || $grade == "H2" || $grade == "H3" || $grade == "H4" || $grade == "S1" || $grade == "S2") {
if ($ctime > strtotime('05:00:00') && $ctime < strtotime('07:30:00')) return "P";
else if ($ctime > strtotime('07:30:00') && $ctime < strtotime('8:30:00')) return "L";
}
else {
if($ctime > strtotime('05:00:00') && $ctime < strtotime('07:15:00'))
return "P";
else if ($ctime > strtotime('07:15:00') && $ctime < strtotime('8:30:00'))
return "L";
}
}
function recordAttendance($conn, $sid, $glid, $scid) {
$sql = mysqli_query($conn, "INSERT INTO tbl_attendance(student_id, gradeLevel_id, section_id, date, arrival_time, status) VALUES ('".$sid."', '".$glid."', '".$scid."', CURDATE(), CURTIME(), '".compareTime(date('H:i:s'),$glid)."')") or die(mysqli_error());
}
$res = mysqli_query($connect, "SELECT * FROM tbl_student WHERE card_id = '$cardID'")or die(mysqli_error());
while($row = mysqli_fetch_array($res,MYSQLI_ASSOC)) {
if (checkAttendance($connect, $row['student_id']))
echo "Already Exist!";
else
recordAttendance($connect, $row['student_id'], $row['gradeLevel_id'], $row['section_id']);
}

Answer 1

It could have several reasons actually, but you'll need to debug to see which is the case.
First start debugging by outputting the values of compareTime to see if they actually work at all. If it doesn't, fix that first.
If that works you could try adding a 'hardcoded' value to your query to see if that gets inserted into your (test) data/table. If that doesn't produce a good result either it might be a case of wrong type in the database. Maybe it's expecting an integer or something else?
You could also extract the function call from the query and put it in a variable, it will provide a bit cleaner and more readable code, as well as it being easier to debug.
p.s.
Did you realise that, in the unlikely event of a time being exactly 7:30:00 or 7:15:00, a person falls between the cracks because you only check for greater or smaller than. Some should also be >= or <=
Might be better to rewrite it to something like this:
function compareTime($grade,$time = ''){
$time = (empty($time))?strtotime(date('H:i:s')):strtotime($time);
$time_5 = strtotime('05:00:00');
$time_715 = strtotime('07:15:00');
$time_730 = strtotime('07:30:00');
$time_830 = strtotime('08:30:00');
if ($grade == "H1" || $grade == "H2" || $grade == "H3" || $grade == "H4" || $grade == "S1" || $grade == "S2") {
if (
$time > $time_730
&& $time < $time_830
){
return "L";
} elseif (
$time > $time_5
&& $time <= $time_730
){
return "P";
}
} else {
if (
$time > $time_715
&& $time < $time_830
){
return "L";
} elseif (
$time > $time_5
&& $time <= $time_715
){
return "P";
}
}
}