PHP | $_POST failing to read value from a dropdown - php

Question

I am new to php, so please do not mind if this is trivial.
I am trying to build a few web pages using php and mysql. The form contains a couple of drop downs and a text input. When the submit(POST) operation is performed, I am trying to insert the values in the mysql DB. Surprisingly I am able to get the values filled for a couple of variables ($doctor, $docFees), but one of them misses out ($spec) and hence a blank entry is getting created. Tried debugging, but an additional pair of fresh eyes can certainly help. Here is the code base that I am trying to work with..
if(isset($_POST['buy-submit']))
{
$pid = $_SESSION['pid'];
$username = $_SESSION['username'];
$email = $_SESSION['email'];
$fname = $_SESSION['fname'];
$lname = $_SESSION['lname'];
$gender = $_SESSION['gender'];
$contact = $_SESSION['contact'];
$doctor=$_POST['doctor'];
$spec=$_POST['spec'];
$email=$_SESSION['email'];
$docFees=$_POST['docFees'];
$appdate=$_POST['appdate'];
$apptime=$_POST['apptime'];
$cur_date = date("Y-m-d");
date_default_timezone_set('Asia/Kolkata');
$cur_time = date("H:i:s");
$apptime1 = strtotime($apptime);
$appdate1 = strtotime($appdate);
if($docFees>0){
//$check_query = mysqli_query($con,"select apptime from appointmenttb where doctor='$doctor' and appdate='$appdate' and apptime='$apptime'");
$check_query = mysqli_query($con,"select count(*) from med_inv where med_name='$spec' and quantity>'$docFees'");
if(mysqli_num_rows($check_query)==1){
$query=mysqli_query($con,"insert into med_sale(med_name,quantity) values('$med_name','$docFees')");
if($query)
{
echo "<script>alert('Your order is successfully placed');</script>";
}
else{
echo "<script>alert('Unable to process your request. Please try again!');</script>";
}
}
else{
echo "<script>alert($doctor);</script>";
echo "<script>alert($docFees);</script>";
echo "<script>alert('Requested Quantity Not available in STOCK!! SORRY! ');</script>";
}
}
else{
echo "<script>alert('Invlaid Quantity specified!!');</script>";
}
}
<div class="tab-pane fade" id="list-home" role="tabpanel" aria-labelledby="list-home-list">
<div class="container-fluid">
<div class="card">
<div class="card-body">
<center><h4>Order a Medicine</h4></center><br>
<form class="form-group" method="post" action="admin-panel.php">
<div class="row">
<div class="col-md-4">
<label for="spec">Medicine Name :</label>
</div>
<div class="col-md-8">
<select name="spec" class="form-control" id="spec" required="required">
<option value="" </option>
<?php
display_meds();
?>
</select>
</div>
<br><br>
<script>
document.getElementById('spec').onchange = function foo() {
let spec = this.value;
console.log(spec)
document.getElementbyID('doctor').value='';
let docs = [...document.getElementById('doctor').options];
docs.forEach((el, ind, arr)=>{
arr[ind].setAttribute("style","");
if (el.getAttribute("data-spec") != spec ) {
arr[ind].setAttribute("style","display: none");
}
});
};
</script>
<div class="col-md-4"><label for="doctor">Price:</label></div>
<div class="col-md-8">
<select name="doctor" class="form-control" id="doctor" required="required">
<option value="" disabled selected></option>
<?php display_xdocs(); ?>
</select>
</div><br/><br/>
<script>
document.getElementById('doctor').onchange = function updateFees(e) {
var selection = document.querySelector(`[value=${this.value}]`).getAttribute('data-value');
document.getElementById('docFees').value = selection;
};
</script>
<div class="col-md-4"><label for="consultancyfees">
Quantity
</label></div>
<div class="col-md-8">
<!-- <div id="docFees">Select a doctor</div> -->
<input class="form-control" type="text" name="docFees" id="docFees" required="required"/>
</div><br><br>
<div class="col-md-4">
<input type="submit" name="buy-submit" value="Purchase Medicine" class="btn btn-primary" id="inputbtn">
</div>
<div class="col-md-8"></div>
</div>
</form>
</div>
</div>
</div><br>
</div>
Functions used
function display_meds() {
global $con;
$query="select distinct(med_name) from med_inv";
$result=mysqli_query($con,$query);
while($row=mysqli_fetch_array($result))
{
$med_name=$row['med_name'];
echo '<option data-value="'.$med_name.'">'.$med_name.'</option>';
}
}
function display_xdocs()
{
global $con;
$query = "select * from med_inv";
$result = mysqli_query($con,$query);
while( $row = mysqli_fetch_array($result) )
{
$username = $row['mrp'];
$price = $row['mrp'];
$spec = $row['med_name'];
echo '<option value="' .$username. '" data-value="'.$price.'" data-spec="'.$spec.'">'.$username.'</option>';
}
}
Values inserted into the table med_sale. First entry was manual for test purpose. So clearly $spec value is not being read from the POST method.
mysql> select * from med_sale;
+----------+----------+
| med_name | quantity |
+----------+----------+
| test | 5 |
| | 5 |
| | 7 |
| | 700 |
| | 4 |
| | 33 |
+----------+----------+
6 rows in set (0.00 sec)

Answer 1

Two problems.
Firstly invalid HTML, missing >:
<option value="" </option>
Secondly, in your display_meds function data-value should be simply value, like so:
echo '<option value="'.$med_name.'">'.$med_name.'</option>';