PHP is a good language to start with for a complete beginners, but you might have problems if you decide to move from PHP to a "bigger" language like C++. C# is a good option too as it's very feature-rich and quite programmer-firendly.
If you're interested in InSim, you might want to learn some basics of network communication too.
PRISM has that covered, all you have to do is have a basic understanding of the API for PRISM and everything else is handled by the backend. This is why I've been saying for like 5 years that plugins are the way to go. It makes programming easy. Granted PIRMS is not 1.0.0 yet, but once it is, man it's going to be sublime!
m8 read the insim.txt thats in ur lfs folder located in doc thats more easy download visual studio c# and download some insims and read codes and your good m8 thats wat i did until i know how to code
I don't think that this is the best approach unless you have at least basic programming experience. InSim.txt is actually a C/C++ header file so unless you know what a struct is, you won't get any useful clue here.
Dygear is right about using some solid library like PRISM or Spark, it can save you a lot of headaches and takes away dealing with the "low level" stuff. But I still think it's a good idea to learn a thing or two about packets and sockets; knowing what's really going on can save you even more headaches
There is a LOT of tutorials for C#, PHP or Python on the web, some better, some worse, I'd start there and once you grasp the basics, get some decent library and start toying with the InSim.