There are many pieces of software on the market that can be used to write and edit HTML and PHP files. Some of the ones I have used include:
1. PHP Expert Editor
3. EvrSoft HTML Editor
4. Macromedia Dreamweaver
They are all good programs. I use PHP Expert Editor mostly when I am writing PHP pages, since it has a built-in engine that can execute the files from within itself (you must have PHP installed on your computer). Evrsoft has the ability to allow you to view the HTML file you are creating in real time. So as you code, you see exactly how the page looks as you go along. HapEdit is a stand-alone editor and as such I am able to carry it anywhere with me, on a jump drive or CD. Macromedia Dreamweaver is very powerful because you can actually design how you want you web pages to look and it automatically creates the HTML code for you. As you can see, they each have a strong point, and as such I use them all.
You can test them and see which suits you better. I am sure you will not be disappointed.