It is reported that only apache can work with PHP script. It seems that there are some throttling issues relating to php-thttpd in which the "POST" cannot work when a long string is trying to pass to the web server.
Please refer to:
I agree with part of this, in that PHP performance under thttpd is pretty poor - I struggled on with php-thttpd on my slug (Unslung) for a few months before finally ditching thttpd for lighttpd (with PHP via FastCGI?) this weekend.
Under thttpd, PHP performance was slow at best, and at worst pages would just not appear - probably due to the 'throttling' issues mentioned above. However, lighttpd/FastCHI?/PHP is much more reliable, and a little faster, though to be fair this set of apps is making the slug work fairly hard as well. At least I can now run PHP applications like TorrentFlux? now, which just didn't work under thttpd.
As you can guess, I would take issue only with the point that Apache is the only HTTP server available for the slug, which can run PHP scripts adequately. I would recommend lighttpd, which has many of Apache's features (including virtual hosting, though I haven't tried this yet) without the 'bloat' - apparently Cherokee is suitable for PHP as well, but I have no experience with that server.
My advice in short: thttpd is fine for basic, static sites with no dynamic content, but if you want PHP on the slug with decent performance and reliability, go for lighttpd with FastCGI?. It's working for me, at the moment at least! - Tim