Kevin Waterson has posted a new tutorial to the PHPro.org website today stepping you through the automation of handing reciprocal links.

This tutorial looks at the process of reciprocal links. That is, links generated from websites that have links to your own page. These links back to a page can be detected from the HTTP REFERER which, in PHP, can be detected via the super global variable $_SERVER['HTTP_REFERER']. Care should be taken when using this variable as it is set from userland and, as such, should not be trusted.

His method stores the linking information (gathered from the referrer) and calls an addLinks method that checks to ensure the page format is valid and that it's a real site before putting it into the table. Complete code for this, a fetch method and a simple database layer to put it on top of are included.

There's a tutorial over on mpwebwizard.com that's been updated and talks about using a mirror to handle hits from a popular website (like digg or slashdot).

caching services such as coral content distribution network provide an alternative for when your site goes down, but why wait until it gets to that stage? why not just send all your hits from high-end websites to the coral cache version? well, there isn't a good reason not to, so i'll show you how to do it automatically.

He provides the simple script that looks for certain sites in the "HTTP_REFERER" value of incoming calls and pushes them off to the cached location with a header() redirect. The whole thing is only 12 lines, not counting the $sites array.