PHP is easy to learn and the documentation is extensive. But it is very easy to do things wrong in PHP, mostly because people learning PHP do a lot of copy/paste coding without really understanding the domain they're coding for (in this case, a web browser over the internet).

There are a lot of sites that give information on working with PHP correctly (including http://appwithphp.com/ and http://planet-php.net/), but expect to do a lot of reading and experimenting before getting it right.

I personally didn't care much for Perl as a web language, although it's great for system-level scripting.

I'd add Python to your list of potential languages too. I've been having a lot of fun with it lately :)