The CREDITS etiquette for php extensions isn't quite what you describe here. The accepted practice (there are no rules) is this:
If you have the karma and have made some contribution(s), and you feel that it was worthwhile, you simply add yourself to the CREDITS file for the relevant extension. If you're unsure, you will usually ask someone else that is listed there if it would be okay to be added.
If other people disagree, an argument^H^H^H^H^H^Hdiscussion will ensue to resolve the matter. (this has not ever happened, AFAIK)
IMO, it would be nice to extend this idea to phpdoc and have some kind of author tags per file in the doc tree and allow the authors/translators to use them to credit themselves.
Sure, this will work in the future. But you would not expect people who have not been around for years here, to add themselfs now :) I have not proposed using this commit number based (and human edited) method to last, but just as an initial start to credit significant contributions. We can start to add DocBook authoring information into the files too, but that will hardly work for older contributions.
BTW people here have mostly seemed to be shy to propose themselfs, maybe because this have never been a practice here from the start. I hope this will change if they see me adding myself as an editor, or see Philip adding himself as an past active author :)
Goba