リクエストヘッダに書くメソッドがHTTP_Request にある。

    /**

    * Sets a proxy to be used

    *

    * @param string     Proxy host

    * @param int        Proxy port

    * @param string     Proxy username

    * @param string     Proxy password

    * @access public

    */

    function setProxy($host, $port = 8080, $user = null, $pass = null)

    {

        $this->_proxy_host = $host;

        $this->_proxy_port = $port;

        $this->_proxy_user = $user;

        $this->_proxy_pass = $pass;
        if (!empty($user)) {

            $this->addHeader('Proxy-Authorization', 'Basic ' . base64_encode($user . ':' . $pass));

        }

    }
    /**

    * Sets basic authentication parameters

    *

    * @param string     Username

    * @param string     Password

    */

    function setBasicAuth($user, $pass)

    {

        $this->_user = $user;

        $this->_pass = $pass;
        $this->addHeader('Authorization', 'Basic ' . base64_encode($user . ':' . $pass));

    }