Online PHP editor | output for tiUqB

<?php <?php session_start(); // ***************************************** // // ********** DECLARE VARIABLES ********** // // ***************************************** // $username = 'username'; $password = 'password'; $random1 = 'secret_key1'; $random2 = 'secret_key2'; $hash = md5($random1.$pass.$random2); $self = $_SERVER['REQUEST_URI']; // ************************************ // // ********** USER LOGOUT ********** // // ************************************ // if(isset($_GET['logout'])) { unset($_SESSION['login']); } // *********************************************** // // ********** USER IS LOGGED IN ********** // // *********************************************** // if (isset($_SESSION['login']) && $_SESSION['login'] == $hash) { ?> <p>Hello <?php echo $username; ?>, you have successfully logged in!</p> <a href="?logout=true">Logout?</a> <?php } // *********************************************** // // ********** FORM HAS BEEN SUBMITTED ********** // // *********************************************** // else if (isset($_POST['submit'])) { if ($_POST['username'] == $username && $_POST['password'] == $password){ //IF USERNAME AND PASSWORD ARE CORRECT SET THE LOG-IN SESSION $_SESSION["login"] = $hash; header("Location: $_SERVER[PHP_SELF]"); } else { // DISPLAY FORM WITH ERROR display_login_form(); echo '<p>Username or password is invalid</p>'; } } // *********************************************** // // ********** SHOW THE LOG-IN FORM ********** // // *********************************************** // else { display_login_form(); } function display_login_form(){ ?> <form action="<?php echo $self; ?>" method='post'> <label for="username">username</label> <input type="text" name="username" id="username"> <label for="password">password</label> <input type="password" name="password" id="password"> <input type="submit" name="submit" value="submit"> </form> <?php } ?>