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If you are looking for an affiliate program to participate in, I'm not sure why it would matter what the company scripts in. You send an affiliate to their site and don't have to worry about anything from there.
On the other hand, if I misread your question and you have a site about PHP and are looking for a related to affiliate program, you might have some options. PHP itself is free, so hard to generate income from directly. It seems like marketing PHP books and resources using Amazon and Google Adsense would be your best bets. There may be a tech heavy site somewhere that focuses on PHP resources, but nothing comes immediately to mind.
There are also 8 programs listed at GetAScript.com under PHP > Affiliate Programs. That might be a good place to start.