You will of course add your extra info in the client script, on this line:

 var highscore_url = addScoreUrl + "name=" + WWW.EscapeURL(name) + "&score=" + score + "&hash=" + hash + "&extra_stuff="+extra_stuff

Then you need to add to the PHP script:

$extra_stuff = mysql_real_escape_string($_GET['extra_stuff'], $db);   

  $query = "insert into scores values (NULL, '$name', '$score', $extra_stuff);"; 

And make sure you add fields to your database too.

You can test your PHP by just hitting it with a web browser.

Allright, I finally got this working. I'll post the full code here so that others can benefit from this in the future

PHP:

<?php 
        $db = mysql_connect('mysql.host.com', 'username', 'password') or die('Could not connect: ' . mysql_error()); 
        mysql_select_db('database') or die('Could not select database');

        // Strings must be escaped to prevent SQL injection attack. 
        $name = mysql_real_escape_string($_GET['name'], $db); 
        $score = mysql_real_escape_string($_GET['score'], $db);
        $email = mysql_real_escape_string($_GET['email'], $db); 
        $date = date("d/m/Y");
        $hash = $_GET['hash']; 

        $secretKey="replacewithyourown"; # Change this value to match the value stored in the client javascript below 

        $real_hash = md5($name . $score . $secretKey); 

        if ($real_hash != $hash) {
        die('haha, try again sucker');  
        }

        if($real_hash == $hash) { 
            // Send variables for the MySQL database class. 
            $query = "insert into scores values (NULL, '$name', '$score', '$email', '$date');"; 
            $result = mysql_query($query) or die('Query failed: ' . mysql_error()); 
        } 
?>

Javascript:

private var secretKey="replacewithyourown"; // Edit this value and make sure it's the same as the one stored on the server
var addScoreUrl="http://replacewithyourown.com/addscore.php?"; //be sure to add a ? to your url
var highscoreUrl="http://replacewithyourown.com/display.php";    


function postScore(name, score, email) {
    //This connects to a server side php script that will add the name and score to a MySQL DB.
    // Supply it with a string representing the players name and the players score.
   var hash=md5functions.Md5Sum(name + score + secretKey);

   var highscore_url = addScoreUrl + "name=" + WWW.EscapeURL(name) + "&score=" + score + "&email=" + WWW.EscapeURL(email) + "&hash=" + hash ;

    // Post the URL to the site and create a download object to get the result.
    hs_post = WWW(highscore_url);
    yield hs_post; // Wait until the download is done
    if(hs_post.error) {
        print("There was an error posting the high score: " + hs_post.error);
    }
}

// Get the scores from the MySQL DB to display in a GUIText.
function getScores() {
    gameObject.guiText.text = "Loading Scores";
    hs_get = WWW(highscoreUrl);
    yield hs_get;

    if(hs_get.error) {
        print("There was an error getting the high score: " + hs_get.error);
    } else {
        gameObject.guiText.text = hs_get.data; // this is a GUIText that will display the scores in game.
    }
}

MySQL Table:

CREATE TABLE `scores` (
   `id` int(10) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
   `name` varchar(15) NOT NULL DEFAULT 'anonymous',
   `score` int(10) UNSIGNED NOT NULL DEFAULT '0' ,
   `email` varchar(255) NOT NULL DEFAULT 'anonymous',
   `date` varchar(15) NOT NULL DEFAULT 'anonymous'

Assets/all/score/score.js(36,13): BCE0005: Unknown identifier: 'Md5'. error how can souve?

I have set up the db and its working with Server Side Highscores script. i am getting stuck in adding data automatically eg when a coin is collected in a game a score is added live onto the sql . any suggestions ?