PHP - Getting The Value Of A Specified String.

In PHP Version 8.0 shows error as :
PHP Fatal error:  Uncaught TypeError: Unsupported operand types: string * string 
String is as under :
$TAXVALUE= round($QNTY*($PRICE- ($PRICE*$DISC/100)),2);

In previous versions of PHP it does not show any error.

Please resolve the issue.

    function getPath($path)
    {
      switch($path){
        case 'classes': $path=__DIR__;break;
        case 'application': $path=dirname(__DIR__);break;
        case 'root': $path=dirname(dirname(__DIR__));break;
        case 'twig': $path=dirname(dirname(__DIR__)).'/vendor/autoload.php';break;
        case 'lib': $path=dirname(__DIR__).'/lib';break;
        case 'help': $path=dirname(__DIR__).'/lib/help';
        case 'templates': $path=dirname(__DIR__).'/lib/templates';
        case 'htdocs_base': $path=dirname(dirname(__DIR__)).'/html';
        case 'resources_base': $path=dirname(dirname(__DIR__)).'/user_resources';
        // About 10 more
        default: throw new Exception("Path {$path} not valid.");
      }
      return $path;
    }

<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>" method="POST" autocomplete="on">
            <div class="ui-contact-form ">
                <span class="icon-user ui-contact-icons"></span><label>Name: </label><input class="input-name"  type="text" name="name"  autofocus/>
            </div>
            <div class="ui-contact-form">
                <span class="icon-list ui-contact-icons"></span><span>Service of Enquiry: </span>
                <div id="radio" class="btngrp-service" name="btngrp-service1" >
                    <input type="radio" id="radio1" name="btngrp-service" value=1><label for="radio1" class="btngrp-service">Moving</label>
                    <input type="radio" id="radio2" name="btngrp-service" value=2 checked="checked"><label for="radio2" class="btngrp-service">Delivery</label>
                    <input type="radio" id="radio3" name="btngrp-service" value=3><label for="radio3" class="btngrp-service">Accounting</label>
                    <input type="radio" id="radio4" name="btngrp-service" value=4><label for="radio4" class="btngrp-service">IT</label>
                    <input type="radio" id="radio5" name="btngrp-service" value=5><label for="radio5" class="btngrp-service">Others</label>
                  </div>
            </div>
                <div class="ui-contact-form">
                    <span class="icon-envelop ui-contact-icons"></span><label>E-Mail: </label><input type="email" name="email" />
                </div>
                <div class="ui-contact-form">
                    <span class="icon-phone ui-contact-icons"></span><label>Contact No.: </label><input type="tel" name="contactno" />
                </div>
                <div class="ui-contact-form">
                    <span class="icon-info ui-contact-icons"></span><label>Feedback / Enquiries </label><textarea rows="5" cols="10" name="enquiry" placeholder="Enter your questions here!" ><?php echo htmlspecialchars($enqContent); ?></textarea> 
                </div>
                <input type="submit"/>
            </form>

if (isset($_GET['delSpeed']) && isset($_GET['delWeight'])) {
    $delSpeed = $_GET['delSpeed'];
    $delWeight = $_GET['delWeight'];
    $enqContent = 'I would like to enquire about a delivery order weighing ';
    $enqContent.= $delWeight .'KG and would require '.$serviceText. ' shipping.';
} else {
    $enqContent = '';
}

$nameErr  = $emailErr = $contactErr = $enquiryErr = "";
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$valid = true;
var_dump($enqContent); <-- already cut off here

if (empty($_POST["name"])) {
    $nameErr = "<span>Please enter a valid name</span>";
    $valid = false;
}
else {
    $name = $_POST["name"];
    $_SESSION['name']=$name;
}

if (empty($_POST["email"]))  { 
    $nameErr = "<span>Please enter a valid email</span>";
    $valid = false;
    $emailErr = "Missing";
}
else {
    $email = $_POST["email"];
    $_SESSION['email'] = $email;

}
if (empty($_POST["contactno"])) { 
    $nameErr = "<span>Please enter a valid contact number.</span>";
    $valid = false;
    $error = "error";
}
else {
    $contactNum = $_POST['contactno'];
    $_SESSION['contactno'] = $contactNum;
}

if(empty($_POST['enquiry'])) {
    $nameErr = "<span>Please enter valid content to help us serve you better.</span>";
}
else {
    $enquiry = $_POST['enquiry'];
    //$_SESSION['enquiry'] = $enquiry;
    var_dump($enquiry);
}
if($valid) { 
    //trim input
    print_r($_POST);
    $serviceType = $_POST['btngrp-service'];
    $_SESSION['btngrp-service'] = $serviceType;
    //header('Location: http://localhost/ppsv2/submit.php');
}

I would like to enquire about a delivery order weighing 12KG and would%.