How can I have a reset button in PHP using session?

[idontknowphp]

I want to change the a href to refreshing the session, how can I do that?

<form method="post" action="tryguess.php">

        <input type="text" id="guess" name="guess">

        <input type="submit" value="submit">

        <a href="trynumber.php"><input type="submit" value="reset"></a>

    </form>

<?php
session_start();
 
// Removing session data
if(isset($_SESSION["number"])){
    unset($_SESSION["number"]);
header('Location: trynumber.php');
}
?>