Issue in implementing Simplify payment gateway in php

iam doing a project in php. i need to integrate simplyfy payment gate way in my project

what i did is

based on this documentation - https://www.simplify.com/commerce/docs/tutorial/index i worked

step 1 i have added a form to get debit card details like below

<!-- <h1>Charge  with Simplify Commerce</h1> -->
<form id="simplify-payment-form" action="" method="POST">
    <!-- The  amount is set on the 
server side -->
    <div>
        <label>Credit Card Number: </label>
        <input id="cc-number" type="text" maxlength="20" autocomplete="off" value="" 
autofocus />
    </div>
    <div>
        <label>CVC: </label>
        <input id="cc-cvc" type="text" maxlength="4" autocomplete="off" value=""/>
    </div>
    <div>
   
     <label>Expiry Date: </label>
        <select id="cc-exp-month">
            <option value="01">Jan</option>
            <option value="02">Feb</option>
            
<option value="03">Mar</option>
            <option value="04">Apr</option>
            <option value="05">May</option>
            <option 
value="06">Jun</option>
            <option value="07">Jul</option>
            <option value="08">Aug</option>
            <option value="09">Sep</option>
            
<option value="10">Oct</option>
            <option value="11">Nov</option>
            <option value="12">Dec</option>
        </select>
        <select id="cc-exp-
year">
            <option value="15">2015</option>
            <option value="16">2016</option>
            <option value="17">2017</option>
            <option 
value="18">2018</option>
            <option value="19">2019</option>
            <option value="20">2020</option>
            <option 
value="21">2021</option>
            <option value="22">2022</option>
            <option value="23">2023</option>
            <option 
value="24">2024</option>
        </select>
    </div>
    <button id="process-payment-btn" type="submit">Process Payment</button>
</form>

then i added these 2 script files

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>

<script type="text/javascript" src="https://www.simplify.com/commerce/v1/simplify.js"></script>

then i added these scripts

<script type="text/javascript">
    function simplifyResponseHandler(data) {
        var $paymentForm = $("#simplify-payment-form");
        // Remove all previous 
errors
        $(".error").remove();
        // Check for errors
        if (data.error) {
            // Show any validation errors
            if (data.error.code == "validation") {
          
      var fieldErrors = data.error.fieldErrors,
                        fieldErrorsLength = fieldErrors.length,
                        errorList = "";
                for (var i = 0; i < 
fieldErrorsLength; i++) {
                    errorList += "<div class='error'>Field: '" + fieldErrors[i].field +
                            "' is invalid - " + fieldErrors[i].message + 
"</div>";
                }
                // Display the errors
                $paymentForm.after(errorList);
            }
            // Re-enable the submit button
            $("#process-
payment-btn").removeAttr("disabled");
        } else {
            // The token contains id, last4, and card type
            var token = data["id"];
            // Insert the token into 
the form so it gets submitted to the server
            $paymentForm.append("<input type='hidden' name='simplifyToken' value='" + token + "' />");
            // Submit 
the form to the server
            $paymentForm.get(0).submit();
        }
    }
    $(document).ready(function() {
        $("#simplify-payment-form").on("submit", 
function() {
            // Disable the submit button
            $("#process-payment-btn").attr("disabled", "disabled");
            // Generate a card token & handle the 
response
            SimplifyCommerce.generateToken({
                key: "YOUR_PUBLIC_KEY",
                card: {
                    number: $("#cc-number").val(),
            
        cvc: $("#cc-cvc").val(),
                    expMonth: $("#cc-exp-month").val(),
                    expYear: $("#cc-exp-year").val()
                }
            }, 
simplifyResponseHandler);
            // Prevent the form from submitting
            return false;
        });
    });
</script>

then i added

<?php
 
include("./assets/simplify/lib/Simplify.php");
 
Simplify::$publicKey = 'my public key';
Simplify::$privateKey = 'my private key';
 
$payment = Simplify_Payment::createPayment(array(


        'reference' => '7a6ef6be31',
        'amount' => '1000',
        'description' => 'payment description',
        'currency' => 'USD',
        'token' => '[TOKEN ID]'
));
 
if ($payment->paymentStatus == 'APPROVED') {
    echo "Payment approved\n";
}
else{
    echo"failed";
}
 
?>

now whats my issue is i ran the file. it is working. it is asking the debit card details, but after filling the sandbox details the page is not redirecting to any other page no error in console,

so how i can move further, after filling the details, where it will be redirected. i referred video tutorial but i cant get any video tutorial.

Kindly some one help