BTW I signed up for "principles of software development" course. It starts next week.
Good. irrespective of language you are learning, I suggest you to go through - http://www.norvig.com/21-days.html . This article helped me re-focus and become a better developer. It's really important to pickup good habits from early stages. Happy coding.
I cannot find the thread any more, but there are others with the same thoughts and problems. And the one advice I give them all is: Practice. Every day. Learn new things, new principles, new ways to use the language. One way to do so in a meaningful way while keeping up motivation is to work on a project. I, myself, started out with projects and worked my way up from there.
If you ever wonder, what stuff you might have to learn for the back-end, you are welcome to take a look at my article about Web Development 101, which, instead of listing concrete frameworks, tells you which principles and technologies you need in order to grasp them all and get even more out of it. For backend, all chapters are useful except the "client" chapter :)
I think Jeffrey Way can be a great source of information, you can follow his screencasts for $10 a month on www.laracasts.com. There are a lot towards the framework Laravel, but there are also more basic PHP courses and OOP courses.
Look for example here, this is actually a free course, so maybe you will be just fine with the freebies for a while :-)
You can practice with a code katas: http://codekata.com/ and see code in github repositories. And the key is practise every day.
Have fun learning PHP!
I recommend you to take a look at Refactoring, and Sourcemaking
Lorefnon
Open Web Enthusiast
Mev-Rael
Executive Product Leader & Mentor for High-End Influencers and Brands @ mevrael.com