Condition statement - php

Question

I am trying to generate a report book based on marks scored by a student. In the form I have a checkbox from which a teacher can tick if a student was absent and if that is the case then the value for the MARK must change to AB and COMMENT as ABSENT, while it is able to change the value to "AB", this code is unable to provide a comment that the student was "ABSENT" instead it puts "FAIL" as a comment. What should I change in the code.
if (isset($_POST['absent']) && (empty($mark)))
{
$mark="AB";
$comment="Absent";
}
if($mark < 101 && $mark >=0)
{ $comment="";
if($grade > 9){
$score="";
if($mark >=75 and $mark <= 100 ){
$score=1;
$comment="Distinction";
}else if($mark >= 70 and $mark <=74){
$score=2;
$comment="Distinction";
}else if($mark >= 65 and $mark <= 69 ){
$score=3;
$comment="Merit";
}else if($mark >= 60 and $mark <=64){
$score=4;
$comment="Merit";
}else if($mark >= 55 and $mark <= 59){
$score=5;
$comment="Credit";
}else if($mark >= 50 and $mark <= 54){
$score=6;
$comment="Credit";
}else if($mark >= 45 and $mark <= 49){
$score=7;
$comment="Pass";
}else if($mark >= 40 and $mark <= 44){
$score=8;
$comment="Pass";
}else if($mark >= 0 and $mark <=39){
$score=9;
$comment="Fail";
}else if($mark=="AB"){
$comment="Absent";
}

Answer 1

Else and If used in this repetative way is pretty inefficient. Here is a suggestion to use switch. In PHP 8+ you can possibly also use match. Switch is more efficient because it only checks the value of the testing variable ($mark) once, rather than repeatedly .
$comment=""; //default.
if (isset($_POST['absent']) && (empty($mark)))
{
$mark="AB";
$comment="Absent"; //default.
}
switch((int)$mark < 101 && $grade > 9) {
case in_array($mark, range(75,100)):
$score=1;
$comment="Distinction";
break;
case in_array($mark, range(70,74)):
$score=2;
$comment="Distinction";
break;
case in_array($mark, range(65,69)):
$score=3;
$comment="Merit";
break;
case in_array($mark, range(60,64)):
$score=4;
$comment="Merit";
break;
case in_array($mark, range(55,59)):
$score=5;
$comment="Credit";
break;
case in_array($mark, range(50,54)):
$score=6;
$comment="Credit";
break;
case in_array($mark, range(45,49)):
$score=7;
$comment="Pass";
break;
case in_array($mark, range(40,44)):
$score=8;
$comment="Pass";
break;
case in_array($mark, range(0,39)):
$score=9;
$comment="Fail";
break;
}