If you somehow managed to make it this far without touching a computer, please refer to at least a few of the previous 25 chapters. Humans tend to learn very well by physically doing what they've learned. Go back and pick up a chapter or two that pique your interest and feel free to experiment with the code. The adage "You get out what you put in" has never been more appropriate.
This should ring true even if you've scrupulously read every paragraph and run every application. After all, you're sure to have experienced a thought that starts with: "What happens if ...?" Don't know the answer? Can't find it in the documentation? Experiment. There is no shame in breaking code by exploring boundaries, and by now your PHP skills should be up to a critical point. You can dig yourself out of any hole that you've managed to get yourself into.
This is an important distinction. Digging yourself out of a hole by using your technical skills, leveraging unit tests, and pondering the how's and why's means that your education can continue and, we hope, extend itself beyond the technical realm.