If you are speaking of dynamic web design (you mentioned PHP) try
It's power is smalltalk - either visual works or squeak
If you are looking into programming languages, look into squeak. See the
link above for more than my brief intro here, but also the homepage for
The complete system is open and at your disposal for modifying,
inspecting, learning, debugging, creating, etc.
Squeak runs on many platforms and the image is bit-identical for all
platforms (although there may be some a plugin that only runs on only
one or a few platforms - but I don't know of any off hand.)
Developers see: http://squeak.org/Features/Development/
I'd be happy to answer any questions about squeak.