Display the username of logged in User

the login form in login.html 
<!--LOGIN FORM-->
form name="login-form" class="login-form" action="login.php" method="post">

<!--HEADER-->
    <div class="header">
    <!--TITLE--><h1>Login Form</h1><!--END TITLE-->
    </div>
    <!--END HEADER-->
	
	<!--CONTENT-->
<div class="content">
   <!--USERNAME-->
<input name="user" type="text" class="input username"     value="Username" önfocus="this.value=''" />
   <!--END USERNAME-->

     <!--PASSWORD-->
<input name="pass" type="password" class="input password" value="Password"  önfocus="this.value=''" /><!--END PASSWORD-->
    </div>
    <!--END CONTENT-->
    
    <!--FOOTER-->
    <div class="footer">
         <!--LOGIN BUTTON-->
	<input type="submit" name="submit" value="Login" class="button" />
	<!--END LOGIN BUTTON-->
	
    <!--REGISTER BUTTON-->

        <a >Register</a>
	<!--END REGISTER BUTTON-->
	

	
	
    </div>
  
</form>
<!--END LOGIN >

<?php

define('DB_HOST', 'localhost');

define('DB_NAME', 'mydb');

define('DB_USER','root');

define('DB_PASSWORD','');

 

$con=mysql_connect(DB_HOST,DB_USER,DB_PASSWORD) or die("Failed to connect to MySQL: " . mysql_error());

$db=mysql_select_db(DB_NAME,$con) or die("Failed to connect to MySQL: " . mysql_error());

/*

$ID = $_POST['user'];

$Password = $_POST['pass'];

*/

function SignIn()

{

session_start();   //starting the session for user profile page

if(!empty($_POST['user']))   //checking the 'user' name which is from Sign-In.html, is it empty or have some text

{

    $query = mysql_query("SELECT *  FROM websiteusers where userName = '$_POST[user]' AND pass = '$_POST[pass]'") or die(mysql_error());

    $row = mysql_fetch_array($query) or die(mysql_error());

    if(!empty($row['userName']) AND !empty($row['pass']))

    {

        $_SESSION['userName'] = $row['pass'];

        echo "SUCCESSFULLY LOGIN TO USER PROFILE PAGE...";
        mysql_query("UPDATE websiteusers SET login=1 WHERE userName = '$_POST[user]' AND   pass = '$_POST[pass]'");
	    header('Location: home.html');

 

    }

    else

    {

        echo "SORRY... YOU ENTERD WRONG ID AND PASSWORD... PLEASE RETRY...";

    }

}

}

if(isset($_POST['submit']))

{

    SignIn();

}

 

?>