PHP HTTPクライアントでBASIC認証

$pass_digest = base64_encode( $user.":".$pass );
$req = new HTTP_Request();

$req->setURL($url);

$req->addHeader('Authorization','Basic '.$pass_digest);

$req->addHeader('Cache-Control', 'no-cache');

$req->setMethod(HTTP_REQUEST_METHOD_POST);

$req->addPostData( "post1", $post1 );

$req->addPostData( "post2", $post2 );

$req->addPostData( "post3", $post3 );
$res = $req->sendRequest();

if (PEAR::isError($res)) {

...

}