Any PHP coders around here?

[Joe 90]

I'm having issues with errors and i can't stand debugging PHP.

i've written a forum, got all the code, forms, scripts etc sorted. but obviously when you put it up it moans.

http://homepages.shu.ac.uk/~mwalker8/bbad/forum/

The registration works fine, login doesnt no idea why at the moment.

main problem though i guess;

Fatal error: Call to undefined function mysqli_connect()

so i'm using that standard sqli function like this;

$con = mysqli_connect($host,$user,$passwd) or die(mysql_error());

does anybody know exactly what this function does? its obviously in compatible with the uni server so i guess i need to write it out myself as it were.


also, theres that login that doesn't work...
so my code;
login form

<?php if (isset($login_error)) { ?>
There was an error: <?php echo $login_error; ?>, please try again.
<?php } ?>
<form action="login_submit.php" method="post">

<b>Username:</b> <input type="text" size="20" maxlength="20" name="username"
<?php if (isset($_POST['Username'])) { ?> value="<?php echo $_POST['Username']; ?>" <?php } ?>/><br />

<b>Password:</b> <input type="password" size="20" maxlength="10" name="Password" /><br />

<input type="submit" name="submit" value="Login" />
</form>

login script;

<?php

// Include start file
include 'start.php';

if (!isset($_POST['submit']))
{
     // Show the form
     include 'login.php';
     exit;
}
else
{
     // Try and login with the given Username & pass
     $result = user_login($_POST['Username'], $_POST['Password']);

     if ($result != 'Correct')
     {
          // Reshow the form with the error
          $login_error = $result;
          include 'login.php';
     }
     else
     {
          echo 'Thank you for logging in, please <a href="login.php">click here</a>.';
     }
}
?>

and those login functions;

function user_login($Username, $Password)
{
     // Try and get the rand from the database using the Username
     $query = "select rand from forum_Users where Username='$Username' limit 1";
     $result = mysql_query($query);
     $user = mysql_fetch_array($result);

     // Using the rand, encrypt the given Password to see if it
     // matches the one in the database
     $encrypted_pass = md5(md5($Password).$user['rand']);

     // Try and get the user using the Username & encrypted pass
     $query = "select UserID, Username from forum_Users where Username='$Username' and Password='$encrypted_pass'";
     $result = mysql_query($query);
     $user = mysql_fetch_array($result);
     $numrows = mysql_num_rows($result);

     // Now encrypt the data to be stored in the session
     $encrypted_id = md5($user['UserID']);
     $encrypted_name = md5($user['Username']);

     // Store the data in the session
     $_SESSION['UserID'] = $UserID;
     $_SESSION['Username'] = $Username;
     $_SESSION['encrypted_id'] = $encrypted_id;
     $_SESSION['encrypted_name'] = $encrypted_name;

    if ($numrows == 1)
    {
        return 'Correct';
    }
    else
    {
        return false;
    }
}

function user_logout()
{
     session_unset ();
     session_destroy ();
}

function is_authed()
{
     // Check if the encrypted Username is the same
     // as the unencrypted one, if it is, it hasn't been changed
     if (isset($_SESSION['Username']) && (md5($_SESSION['Username']) == $_SESSION['encrypted_name']))
     {
          return true;
     }
     else
     {
          return false;
     }
}

can anyone see an error? i can't figure it out