Suggestions

1. Poor syntax coloring - I want to specify the color of methods, static functions, classes/interfaces, modificators, etc. While Java IDEs always have it, PHP IDEs do not support it (hm, maybe Zend Studio).
2. Maybe I can't find it but I can't find a classical option "Insert spaces for tabs". I prefer tabs but IDEA seems to put spaces.
3. public function ant then CTRL+SPACE. I can see __construct() and __destruct(). What about __set, __get, __sleep, __wakeup, etc.?
4. You could warn user if a method with @return phpDoc doesn't return anything. And other things known from non-dynamic languages that help the developer.
5. Try to write /** and press enter before a method. The comment has inconsistent indentation.
6. After $_SERVER CTRL+SPACE should hint ["SERVER_NAME"] and other available array keys that can be found in this array.
7. CTRL+Q on method/function shows me: (...) @link http://php.net/manual/en/... - links should be clickable.
8. CTRL+SPACE should hint phpdocs in /** comments.
9. $this-> CTRL+SPACE doesn't hint member variables (properties).
10. public fu CTRL+SPACE should put "function " - with a space at the end.
11. class Executor ex CTRL+SPACE suggests exception, extends and exit.
12. Strings can be written using ' and ". So, pressing ' should have such an affect: ''.
13. If a user write echo "something" IDEA should hint him to change " into ' because of performance reasons.

I will submit more suggestions and bugs soon.

P.S. Your WYSIWYG editor does not work on Opera 10. Now I use Epiphany but this editor is slow, backspace works with a delay. I feel like I was working on Pentium 150Mhz.
P.S.2 In text mode after submitting you could convert \n into <br> automatically. Or, what's better, convert plain text into html while reading the forum - in case a user wants to edit his comment. I recommend Markdown parser for this.