index.php

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Stripe Example</title>
</head>
<body>
    <h1> Example </h1>
    <form action="checkout.php" method="post">
       <p>T-Shirt</p>
       <p><strong>US $20.00</strong></p>
       <button>Pay</button>
    </form>
</body>
</html>