Well for a start PHP is huge! Plus the fact it can work with so many different plugins now, I don't believe there'll be anyone on the planet that will know every single part of the full PHP language (inc. plugins, etc..), however for all the basic starting points, I'd suggest going to Tizag (http://www.tizag.com/phpT/), they have a load of basic tutorials for you to learn. Plus also feel free to have a ganders over on Good-Tutorials' PHP section (http://www.good-tutorials.com/tutorials/php). Hope that helps.
To use PHP on your own computer (to test things), then you can either install AppServ (http://www.appservnetwork.com/) or Xampp (http://www.apachefriends.org/en/xampp-windows.html). I personally have AppServ running on my computer. Then to make PHP files you just open Notepad do your coding in there and save the files with ".php" instead of ".txt"