Is php and mysql really all I need for a professional database driven site?

[Tobin]

Building a large website with user accounts that will handle online payments

[Ruan Caiman]

It works for a lot of sites, one often cited by PHP/MySQL fans is facebook:
http://www.makeuseof.com/tag/facebook-wo...explained/
Although they use their own flavors of both, they started out with the canned ones.

Here's some more PHP sites, I'd guess at least some of them use mysql:
http://susprod.com/famous-sites-that-use-php/