Connecting forum board accounts to front page of my website

{
    // username and password and email sent from form
    $username=$_POST['username'];
    $password=$_POST['password'];
    $user_email=$_POST['email'];
    
    // CHECK YOUR $_POST VARIABLES TO MAKE SURE THEY'RE VALID.
    
    if ($tests==false) // TOTALLY GENERIC, YOU WILL HAVE TO RUN YOUR OWN TESTS
    {
        header("location: error.php");
    }
    else    
    {
        // PHPBB requires this so it doesn't kick you out of the pages or produce an error
        define('IN_PHPBB', true);
        $phpbb_root_path = 'forums/';
        $phpEx = substr(strrchr(__FILE__, '.'), 1);
        include($phpbb_root_path . 'common.php');
        include($phpbb_root_path . 'includes/functions_user.php');
        include($phpbb_root_path . 'includes/ucp/ucp_register.php');


        // Forum Database Variables
        $host="yourhost.yourhostdomain.com"; // Host name
        $dbusername="username"; // Mysql username
        $dbpassword="databasepassword"; // Mysql password
        $db_name="databasename"; // Database name
        $users_tbl="phpbb_users"; // Table name for PHPBB Users
        $group_tbl="phpbb_user_group"; // Table Name for PHPBB Groups

        // Connect to server and select database
        mysql_connect("$host", "$dbusername", "$dbpassword")or die("cannot connect");
        mysql_select_db("$db_name")or die("cannot select DB");

        // A check to see if the username is unique
        $sql="SELECT * FROM $users_tbl WHERE username='$username'";
        $result=mysql_query($sql);
        $count=mysql_num_rows($result);
    
        // A check to see if the email is unique
        $sql2="SELECT * FROM $users_tbl WHERE user_email='$user_email'";
        $result2=mysql_query($sql2);
        $count2=mysql_num_rows($result2);

        if($count==1)
        {
            header("location: error.php");
        }
        elseif($count2==1)
        {
            header("location: error.php");
        }
        else
        {

    $sql_ary = array(
      'username'     => $username,
      'username_clean'  => $username_clean,
      'user_password'   => phpbb_hash($password),
      'user_pass_convert' => 0,
      'user_email'    => $user_email,
      'user_email_hash'  => crc32(strtolower($user_email)) . strlen($user_email),
      'group_id'     => 2,
      'user_type'     => 0,
    );
  user_add($sql_ary);
        }
    }
}

<?php
if ($user->data['user_id'] == ANONYMOUS) {
?>
  <form action="./forum/ucp.php?mode=login" method="post">
  <label for="username">Username:</label>
  &nbsp;
  <input type="text" name="username" id="username" size="20" title="Username" />
  <label for="password"><br>
  Password:</label>
  &nbsp;
  <input type="password" name="password" id="password" size="20" title="Password" />
  <input type="hidden" name="redirect" value="./index.php" />
  <br>
  <input type="submit" name="login" value="LOGIN" />
  </form>         

<?php }
else
{
 echo $user->data['user_name']; //This line does not work, I was just testing things
 echo "You are logged in."; // same here, edit the output as you wish
}
?>