Depends what's your orientation? Web design or back-end? Any way start with basics , take a good book do the examples then try to make your own project. Hm... Start learning PHP OOP and jQuery(AJAX & JSON).
The best way to learn the programming language by creating the programs. Practice to create programs on regular basis is best and easiest way of learning programming languages. When i started to learn about php, I don't know nothing about this language. I was always using to search on Internet when any problem is occur. But now i am the professional of PHP within the 6 or 7 months.
w3schools has some good tutorials, lynda.com (not free), and personally I like to sign up to forums like this one and try to find the answers to other people's problems. it gives me programs to figure out and troubleshoot without trying to come up with a bunch of programs on my own.
Yes, the only concern with learning on your own is making sure that your sources are current. For example, lynda.com has some great videos, but the essentials series is from 2007 and a fair bit has changed since then. For example, they advocate the use of the mysql_ functions that are now deprecated in favor of mysqli_ or pdo etc. When using multiple sources you're likely to run into more inconsistencies and outdated methods. That's why real time resources like forums are my favorite, as better ways to do things are figured out or made, you find out about them a little faster.