Is it possible to determine whether the user has Flash Player installed, and what level?

I would like to use more Flash, adding extra layers of functionality and design, but not to leave anyone out.

I would also consider HTML or Javascript, if anything works really well.

Ciao and TIA

http://www.sitepoint.com/print/techniques-unearthed
http://www.adobe.com/support/flash/h...vaplugs04.html
http://www.adobe.com/devnet/flash/ar...swfobject.html

Great links, but how do you use these methods to control what you do in PHP? That's the bit where I get confused as PHP is Server Side and not client side, naturally. THerefore, is it possible to use a method of Flash player detection to control what is done with PHP?