Learn PHP in 5 minutes by Igor Carrasco
Learn PHP in 5 minutes! Just in 3 basic steps!
It shows the most basic functions but those are the ones you really need to get started doing something useful.
In only three steps you will be familiar enough to start using it for your needs.
Click Step1 to start.
WAMP (for windows), LAMP (for linux), or MAMP (for Mac OS X) if you just want to have it up and running in no time and without much trouble.
For more complex informations on how to install PHP here is a link.