Bujji, there's nothing magical about askmeflash.com. It's a straightforward site that handles information in, information out with a user management system as any simple web application does. I'd recommend reading a book about building CMS's for the basic concepts, because in essence it's the same thing. This is the one that got me started way back when: http://www.sitepoint.com/books/phpmysql4/
As for frameworks, if you're going PHP/MySQL as you've mentioned, the two frameworks that seem to dominate the landscape today are Zend Framework (framework.zend.com) and Code Igniter (codeigniter.com) Personally, I wouldn't attempt either without a basic knowledge of the ins-and-outs of PHP and OO concepts. Zend especially is very powerful but can get confusing in the beginning....