Hiding a Login Form after successful login

Hiding a Login Form after successful login

I'm extremely new to jQuery so please bear with me.
I've made a form that allows the user to type in their username and password, this form is then submitted to login.php which then checks the user's inputted info with a mysql database
i want to make it so that if the user is logged it, the login form doesn't show up.
i am using session variables (not sure if tht's relevant)
Please let me know if there is any more code i should post
  2. <?php session_start();
  3. $valid = $_SESSION['valid'];
  4. ?>

  6. <html>
  7. <head>
  8. <title> Login </title>
  9. <script type='text/javascript' src='http://localhost:8888/mysite/jquery.min.js'></script>
  10. <script type='text/javascript' src='http://localhost:8888/mysite/script.js'></script>
  11. </head>
  12. <body>
  13. <link rel="stylesheet" type="text/css" href="http://localhost:8888/mysite/form.css" />

  15. <script src="http://localhost:8888/mysite/nav.js"></script>

  17. <div id="loginform">
  18. <form action=login.php method=POST>

  20. <label for=username> Username: </label>
  21. <input type=text name=username> <br>

  23. <label for=password> Password: </label>
  24. <input type=password name=password> <br>
  25. <input type=submit value=Login class=button>

  27. </form>
  28. </div>

  30. </body>
  31. </html>