Go all Macromedia. Its the best solution.
If you want a very nice end to end (well as close as you can get) develpment solution for PHP use Dreamweaver MX. If you are going to be working with Flash this is a no brainer.
Dreamweaver MX has some very nice PHP/database connectivity features. Dreamweaver MX does native PHP coding now also. It allows you to setup a sites settings and enter the info about where the site is stored locally and also remotely, then also enter the info of the database server as well as a testing server (the apache/php machine). Once you have it setup for a peticular site it allows you to modify code (PHP/MySQL) in real time! Not like , saving a file and then reloading it. You type a change and it shows you the result as you finish it. Its very nice. It has a split screen mode that enables you to see a output (html rendered like a browser) view as well as the code view of any page at the same time. Modify one and the other updates.
I currently use Dreamweaver MX on 5 different PHP/MySQL sites over 2 servers and it works seamless.
Heres my setup:
(Local)Blue & White G3 500 Running 10.2 with Dreamweaver MX,Flash MX, Fireworks Mx,Photoshop,JaneBuilder1.5 for design and development.
(local) Blue & White G3 400 as a server running OSX 10.2 with Apache w/PHP, MySQL, phpMyAdmin (controling MySQL databases) and using FileSharing over OSX for moving files from Dev machine to this maching.
(remote) Athlon 1700xp Rack server running RedHat Linux 7.3, Apache, MySQL, etc... This is my server for all my live sites. its being hosted on a 10mbit pipe at a datacenter..
This setup works seamlessly with the Macromedia products. One server for deveopment one for hosting one machine for design and layout and coding.
Any way you go I would stay with a mac. Doing PHP work on a PC is a bitch.. With OSX you can install Apache/MySQL/PHP locally if you wanted to for testing or whatever.
Good luck