>>8
You can make all the dangerous mistakes in any environment. It's easier to make them in PHP, but you have to learn about them whatever you choose. If you don't learn about good practices, using something like Rails won't do shit for you if you don't understand you are supposed to sanitize user input, for example.
Remember that >>1 doesn't know HTML yet: with something better, he would have to learn pretty much everything at the same time.