function loginUser($username, $password)
{

    include('assets/con.php');

    /* Set the salt. */
    $salt = 'JwethYGkuuygTYFIYTFrfkuyGUTf75kUY4uyk6';

    /* Apply SHA512 password and salt encryption. */
    $password = hash('SHA512', $password);
    $salt = hash('SHA512', $salt);

    $query = 'SELECT username FROM users WHERE username = ? AND password = ? AND pass_salt = ?';
    if( $statement = $con->prepare($query) )
    {
        $statement -> bind_param( 'sss', $username, $password, $salt );
        $statement -> execute();
        $statement -> store_result();
        $num_row = $statement -> num_rows;
        $statement -> bind_result($username);
        $statement -> fetch();
        $statement -> close();
    }

    else die( "Failed to prepare query." );

    if( $num_row === 1 )
    {
        $_SESSION['userName'] = $username;
        return true;
    }
    return false;
}