Display Loading Image While Page Loads

@kayinja.denis,

Any reason why it takes so long to go through the calculations?

yes,
I've two loops
one for students and the other is for subject, in order to get the students' marks i've to loop into mark table to get marks for each student each subject

PHP Code:

foreach($students as $student){
$studentID = $student->student;
foreach($subjects as $subject){
$subjectID=$subject->subjectID;

$mark=$this->db->query("select * from mark
          where mark.classesID = '$classID' && mark.studentID = '$studentID' 
          && mark.subjectID = '$subjectID' ")->row()->mark;
}
} 


so if I've more than 10 students per class doing more than 5 subjects,
it'll take long to iterate through that mark query,
so that's why I need that loading display but the one i've got is not doing what i want.