I'm now thinking to establish my server-side code in JavaScript, and begin to do all on it, but I want to know about its security and flexibility compared to PHP.
I want to know too, if it can be successfully used to develop things like forum boards, full web-sites and things like this, as PHP does.
Javascript is just now starting to get some presence on the server, with things like ServerJS and nodeJS, but right now, you would probably be best off using PHP for your server side code, and javascript for client-side beautification.