PHP is the most used web development server side language, it is also the easiest to get started with. Websites as large as Facebook use PHP as it is versatile and can be scaled to deal with millions of requests per day with great ease.
Before you run off trying to develop a website for millions you need to learn the basics. Learning PHP and learning to use a PHP framework are two different tasks.
I would suggest learning PHP by learning a PHP framework, that way you don’t have the double learning curve which many new web developers find themselves dealing with. The easiest php framework to learn also has some of the best docs and tutorials by both the officials means and the community – that is the CodeIgniter framework and community.
Now, you have two options either you find some great free CodeIgniter tutorials like the one’s written by Coding Like a Sir (tutorials are written by Nathan from Teckle Digital)or you can pay a premium for web casts and courses provided by Tuts+ (Tuts+ is brought to you by Envato). When I first started developing using PHP I went down the free tutorials route and it was great, I have since gone on to develop websites used by millions. I always felt that bloggers that wrote tutorials were easier to speak to than dealing with a “faceless” web dev course provider – that’s just my opinion though.
Regardless of the option you choose, with PHP you will be able to do the standard Hello World within seconds and move on to building full dynamic websites, with checkouts, login and register functionality and what ever else you need!
If you want directions for more specific tutorials leave a comment below and I will respond with the best tutorials for your needs.