Nicholas,
Yes, PHP is popular and I thinks it's a fine tool. As others noted several times in this thread, if anyone wants to do an ACS port for PHP, we have no problem with that. We in the OpenACS project simply don't have the man power, nor a good reason to do so.
You can run the ACS on AOLserver, which was chosen way back in 1995 far its superb database capabilities. PHP+Apache, despite all their popularity still haven't gotten to where AOLserver was in 1995. As one of the PHP developers noted at the AOLserver list, PHP's threaded implementation still needs lots of work. Not to mention Apache's.
What was AOLserver's big development in the last couple of years? Maybe we should twist the question a little bit: What has been Apache+PHP's big development in the last couple of years that they still haven't matched AOLsever's capabilities that date of 1995?
You can also run ACS or OpenACS in Apache, thanks to mod_aolserver. Learning Tcl takes a day or less for a developer. Is that too much effort? Soon you'll be able to run ACS on IIS. That takes care of 89%+ of the webserver market.
The AOL team does want AOLserver to be supported. Improvement is being done in that area and we'll have a better aolserver.com website soon. AOL controls the official AOLserver release, but AOLserver is a GPL'd product so if anyone wants to fork another project, they can, but nobody has found a good reason to yet.
I think Apache and PHP are great tools, as is AOLserver, but I haven't seen a toolkit for PHP like the ACS yet. Porting and maintaining to PHP would be a big effort, and mostly unnecessary.
