Passing value to database through if else statement - php

Question

My Form Look like this, here i wanted to send grade of Nepali subject database by taking and converting numeric marks from form mepali_th_num but what ever input numeric mark are it only send 'E' Grade to database after conversion of grade. What is wrong in this code mainly in if else part.
<form class="form-horizontal" method="post">
<div class="box-body">
<div class="form-group">
<label for="nepali_th_num" class="col-sm-2 control-label">Nepali(TH)
</label>
<div class="col-sm-2">
<input type="number" class="form-control" id="nepali_th_num"
name="nepali_th_num" step="any" min="0">
</div>
</div>
<div class="box-footer">
<button type="submit" name="btnSave" class="btn btn-
primary">Submit</button>
<button type="reset" class="btn btn-info">Reset</button>
</div>
</form>
my php look like this:
if (isset($_POST['btnSave'])){
$marksdetails = new Marksdetails();
$marksdetails->set('nepali_th_num', $_POST['nepali_th_num']);
$nep_per=((('nepali_th_num')*100)/75);
if($nep_per>=90){
$nepali_th_grade='A+';
}elseif ($nep_per>=80 && $nep_per<90) {
$nepali_th_grade='A';
}elseif ($nep_per>=70 && $nep_per<80){
$nepali_th_grade='B+';
}elseif($nep_per>=60 && $nep_per<70) {
$nepali_th_grade='B';
}elseif($nep_per>=50 && $nep_per<60){
$nepali_th_grade='C+';
}elseif($nep_per>=40 && $nep_per<50){
$nepali_th_grade='C';
}elseif($nep_per>=30 or $nep_per<40){
$nepali_th_grade='D+';
}elseif($nep_per>=20 or $nep_per<30){
$nepali_th_grade='D';
}else{
$nepali_th_grade='E';
}
$marksdetails->set('nepali_th_grade', $nepali_th_grade);
$marksdetails->set('symbol_number', $symbolnumber);
$marksdetails->set('student_name', $studentname);
$status=$marksdetails->checkDuplicate(); //to check duplicate and sql part
is in this
}

Answer 1

nepali_th_num in this line
$nep_per=((('nepali_th_num')*100)/75);
is just a string, its not a variable containing something useful
Try
$nep_per=((($_POST['nepali_th_num'])*100)/75);