I am an experienced PHP and mySQL developer, and recently I've been considering implementing AJAX into some of my future projects. What I am looking for is an easy, simple, yet efficient solution for implementing AJAX into my projects without writing the Javascript code myself from scratch.

I have seen ASP.NET AJAX, which seems to be pretty good, but my experience with ASP is limited. Is there anything similar to ASP.NET AJAX for PHP?

There are all manner of AJAX javascript toolkits out there, usable regardless of your server side library. If you've not already seen and reviewed the following, make them your first visit:

mochikit (my preference) http://www.mochikit.com/
dojo http://dojotoolkit.org/

These are fairly big frameworks that do a lot of things. mochikit I prefer because of the way it was written; its unit tests; and its fairly comprehensive. When I need just a tiny bit of AJAX for a project I roll my own.

What I want to do is implement, say, a AJAX based map and connect it to a mySQL database. The map would then update dynamically, as the user clicks on the map. I would want to implement this in the simplest way possible, yet maintain some sort of flexibility and ease of use.

Can I implement this with mochikit? Or are there other toolkits out there that are better suited for AJAX with web based games?

www.jquery.com

Also, I use AHAH (Asynchronous HTML And HTTP) instead of AJAX, since I rarely require XML as return data..
For more info: http://microformats.org/wiki/rest/ahah