programmermatt wrote:Because I want to know on the PHP side wether they have javascript so I can conditionally output javascript to them or not and they don't have to worry about selecting wether or not they have javascript in their profiles and also allows guests to use the javascript features without logging in.
You don't need to.
If they don't support javascript, their browser will not download the javascript (unless it is inline, and it shouldnt be - it should be a standalone file, so it can be cached!). This is true on IE, Firefox, Konqueror, AND Opera.
Instead, as suggested, you simply put the fallback functionality in a <noscript> tag.
As to detecting it, I always suggest
http://phpsniff.sourceforge.net