How long does it take to get dedicated with programming? I'm 15 and I'd love a job like you!

It really depends on how keen you are to learn and how quickly you pick things up. There's certain things you need to understand (variables, data types, functions, conditions, control structures, classes)... once you understand the basics it's really just a case of applying it to different and now advanced situations. It's a bit like playing with Lego. It doesn't take long to understand how to use it and build small things, you just need more practice and experience to be able to build bigger more advanced stuff, but it's all done using the same bricks. PHP is the bricks, what you can build with it will improve over time. I started properly when I was 16 and when I was 18 I had a job using PHP, by 19 I was working as a junior at a top local agency. Put the work in and you'll be fine.