Download the PHP Manual in CHM format from:
For writing code, there are loads of editors:
PDT (download this for easy installation)
PHP Eclipse (download this for easy installation)
Notepad++ (basic editor, what I use)
Dreamweaver (Commercial, but good to use if you already use it)
Install XAMPP on the root of any of your drives, e.g. C:\ or D:\
This will prevent most of the problems that we come across during development.
Make sure Port 80 is free (e.g. stop IIS) and you do not have MySQL installed or running from before.
Once extracted, go to the folder and double click "xampp-control.exe". Start Apache and MySQL and then go to http://localhost/xampp
To start developing, create your files/sub-folders in the folder C:\xampp\htdocs (assuming you installed on C: root)
The PHP Manual CHM file is probably the best resource I have come across when starting with PHP development. It has loads of tutorials and examples.