Client

• send pingback for given URL to remote URL
• use HTTP_Request2, since it allows to use curl if available and others if not

$pc = new Pingback_Client();
$pc->send($myUrl, $targetUrl);

TODO: error handling. exceptions? simply true/false with $pc->getError()?

Server

• register custom handler
• register custom validator
• provide basic backlinking validator

$ps = new Pingback_Server();
$ps->registerHandler(array($datastore, 'storePingback'));
$ps->registerValidator(array($pingbackValidator, 'checkBlogAge'));
$ps->registerValidator(array($pingbackValidator, 'checkFriendliness'));
$ps->run();

Existing libraries

• http://pear.php.net/package/Services_Pingback
  • bad: uses outdated libraries (HTTP_Request v1, XML_RPC v1, Net_URL v1), not E_STRICT compliant
• https://github.com/tedeh/pingback-php
  • bad: "Client" (Utility) has no state thus has to re-fetch the remote files again and again (isPingbackEnabled, getPingbackServerURL, isBacklinking)
  • you have to extend the server to properly use it
  • no examples
• https://github.com/driedfruit/php-pingback
  • bad: bunch of functions
• Zend Framework 1 has nothing
  • there was a proposal, Zend_Service_Linkback, but it was not finished/included: http://framework.zend.com/wiki/pages/viewpage.action?pageId=13107298
  • http://www.zendframeworkmagazin.de/zf/blog/pingback-mit-dem-zend-framework-1