this will need careful review and there are still some changes in the GD library functionality not merged from PHP to GD version (number of tests are still failing due different output of some functions).
But this at least makes the API complete PHP GD extension wise.
Not sure we need the AA for PHP. Actually PHP never exposed nor used these functions but the other AA functions for line and co.
I would rather not provide the overlay methods as well, they are really not complete and I would hate to have to maintain them forever. GD 2.2 will have a blending API which can be used for the same purposes and will also provide what these functions try to provide. Also if really desired we can add the overlay functions to gd PHP's code.