Someone mentioned NASA, and here is the story:
http://www.mysql.com/news/article-51.html
It's an excellant link to give anyone who wonders if MySQL is worth using. Personally I've yet to find anything it can't do, though some features that I've never seen a good reason to use are apparently missing.
I don't know of anything that MySQL can't do, even if it does require a little round-the-bend ingenuity.
As for PHP, I can't help but wonder why not to use it 😉
However, www.php.net (duh) and of high note is www.zend.com
The Zend Encoder is highly unique, and it's automatically coupled with the Zend Optimizer which makes a properly designed PHP script as fast as any application there is.
The IDE Zend has come up with seems to be extra-ordinarily good too.
If nothing else PHP is easy to learn. The amount of special training and out-sourcing that can be avoided easily off-sets the price of buying PHP.
Then again, it's kind of easy to offset a price of $0 🙂