It doesn't matter if it's PHP or Perl based, or even if it's a Java applet. A combination of applet/script would also work.
However, I'm not looking for a 1,000 word spell checker. It needs to have at least 50,000 words. The ability to add custom word lists would be good too.
Free Spell Checker [spellchecker.com]
It works on any server that supports CGI. Not sure if its any good for you, but I thought I would mention it anyway!
:)
Andreas