validateUsername example

    /** * Validate the current URI from the instance variables. Returns true if and only if all * parts pass validation. * * @return boolean */
    public function valid()
    {
        // Return true if and only if all parts of the URI have passed validation         return $this->validateUsername()
           and $this->validatePassword()
           and $this->validateHost()
           and $this->validatePort()
           and $this->validatePath()
           and $this->validateQuery()
           and $this->validateFragment();
    }

    /** * Returns the username portion of the URL, or FALSE if none. * * @return string */