PHP 掩饰用户名,隐藏某一部分

/**
 * 掩饰用户名
 *
 * @param unknown $username            
 */
function cover_up_username($username)
{
    if (! empty($username)) {
        $patterns = '/^(.{1})(.*)(.{1})$/';
        if (preg_match($patterns, $username)) {
            $username = preg_replace($patterns, "$1*****$3", $username);
        }
    }
    return $username;
}