I do not know of any good online schools for this.
If you want to learn CSS I highly recommend picking up any book by Eric Meyer - http://meyerweb.com/
For a good reference check out w3schools - http://www.w3schools.com/css/css_reference.asp
I learned CSS through a lot of trial and error, and lots of "how would i do this", "how can i make this thing work" and then just hammering my way through it. Google became my best friend.
The key points to understand for creating good CSS are the DOM, the box model, and the difference between inline and block elements. Anything after that is just learning how to bend the rules to make things work the way you want them to.
If you are just learning PHP and still dealing with things like syntax, control flow, arrays, etc, the php.net documentation is really all you need. After that I recommend the following books:
"Advanced PHP Programming" - http://www.amazon.com/Advanced-Php-Prog ... 098&sr=1-3
- I purchased the first version of this book 5 years ago and can't vouch for this one, but the first one has been an invaluable resource for me, and this one looks like a good update.
"Essential PHP Security" - http://www.amazon.com/Essential-PHP-Sec ... 219&sr=1-1
- This one is a bit old, but the lessons and security concerns are still very much important.
I really have to recommend avoiding most php tutorial sites as they do not teach best practices and push out really bad and insecure code.