Web Development
Here are the (mostly free) tools and facilities that I use in developing PHP systems. Feel free to try them out:

• Programmers' Editor - Context
  Context is a good tool that you can customize to make it even better. For more info on customizing the Context setup for PHP to integrate some other tools, click here.
   
• Development IDE - Netbeans (added Mar 29-09)
  I recently started using Netbeans and I am quite happy with it as a replacement for Context for most things. Netbeans is a (free) Sun product that was originally built for Java development. They have now added other languages, including PHP. There seems to be an active developer community developing plug-ins to provide extra features and integration with other products. It also provides support for CSS, HTML MySQL and so forth. It has its own versioning control, test and debug facilities and so forth.  
   
• Version Control - CS-RCS
  CS-RCS is a pretty simple way to keep a repository of your code by version. It can be integrated with Context so you can do everything from one place. I tried some other options but I found them difficult to install, understand and use. CS-RCS is easy to install and very simple to use.
   

• Test Environment - EasyPHP
  EasyPHP is a package that gives you a "LAMP" (Linux, Apache server, MySQL database, PHP) environment in which you can run your PHP programs. It also includes the PHPMyAdmin tool that you can use to manage your MySQL databases. This runs in a Windows environment and simulates Linux. It is vey clean and doesn't interfere with your Windows operating system.

• MySQL Utility - Toad for MySQL (Added Mar 29-09)
  I have been using PHPMyAdmin for most of my Database setup and admin. One of the things it doesn't seem to have is the ability to compare tables (in different databases) and identify changes. Ideally, it would create the Alter statements to syncronize the structure. I searched the net and found quite a few utilities but many weren't free and a couple that I tried didn't want to connect to my databases. Toad for MySQL seems to be a pretty capable free utility that can do the comparison between tables and many other things.

• FTP & Sync: Upload & Download From Your Server
  There are two programs that I use for this. Filezilla is free but you'll have to pay for Beyond Compare 3. The latter program has the ability to compare directories / source libraries and show you the differences in each individual module. It can do this between your local machine and the server or between local or server libraries. I recommend both of them.
  Note: I used to use the BlazeFTP program but I had some problems with it so I switched to Filezilla.
   
• Search a Code Library for a String
  If you want to find all the references to a particular module or where you have used a particular variable, then Agent Ransack can do it.  
   
• Create a Favicon for a WebSite
  A free online tool to convert a picture to a favicon - click here.
   
• Free Code for Download
  One of the advantages of PHP is the huge amount of free (open source) code that you can download and use. There are many sources but I have mostly used Hotscripts and to a lesser degree, SourceForge.
   
• Ajax - JQuery (Added Mar 29-09)
  If you want to build friendlier applications then you will want to add some Ajax to your apps. JQuery can be integrated with PHP quite easily. I looked at lots of different Ajax environments and I decided to go with JQuery. It is pretty easy to use and there are lots of users and examples.
   
• PHP Forums
  There are many forums where you can ask for PHP help. I find that is one of the best. It is very active and there are people on it who can answer most questions (I've even answered a few myself). It also has forums for many other languages so if you're having HTML, CSS or Ajax problems you can get help there as well.
   
• Server
  If you're going beyond local experimentation, then you'll need your own site on a server. You can get a free site from your ISP or from other companies but they probably won't provide you with PHP and MySQL. There are hosting companies out there that sound good and promise a lot but don't always deliver. I have been using ICDSoft for many years now and I'm very satisfied with them. They provide reliable service and very quick support. Their price is reasonable and they can provide more disk space and bandwidth (as part of one of their packages) than you're likely to need. [I am an affiliate but I only recommend them because they do a good job].

PC Development
If there is some development that you want to do for the Windows environment, then these are good tools to use:

• Compiled Basic - Emergence Basic
  Emergence Basic is a very capable development tool tool that is relatively easy to use but can also do some pretty complex stuff. It is a complete development environment that includes an IDE (development interface) and an integrated compiler and linker.
  The developer (Ionic Wind) offers a couple of other options as well: Creative Basic (even simpler) and Aurora (object oriented).  You can do a free-download and there is an online forum for support and code examples.
   
• Windows Scripting - Autoit 3
  Autoit is a Basic-like tool that can do many things but is particularly capable at automating tasks that need to work with the Windows GUI. "It uses a combination of simulated keystrokes, mouse movement and window/control manipulation in order to automate tasks in a way not possible or reliable with other languages." I have recently used it to do some screen-scraping on Internet sites and I find that it is the best tool for this. Unlike some PHP screen-scraping tools, this works through the Browser so it doesn't have to try to simulate some of the more complicated things that the Browser has to do,