I'm trying to find a good environment to building and maintain an existing website. Would Adobe's Dreamweaver be a good purchase as far as coding in PHP, html, jquery, with a mysql database?
Dreamweaver is mostly a waste of money unless the site is static or static mixed with pages that have procedural PHP. And only then the only real features that make it somewhat worth the money are the templating/library item features.
If youre building something with an MVC architecture or using a full blown CMS youre better off an actual IDE (Netbeans, Eclipse, etc..) or a lightweight text editor (Textmate, E, Notepad++, Coda, etc..).
I would recommend checking out open source solutions before putting money down on Dreamweaver. To that end, I would highly recommend the Eclipse IDE for PHP development. You can also get MySQL plugins for Eclipse as well.
No. I've done it myself, and Dreamweaver isn't really suited to PHP/jQuery/MySQL. It will get syntax highlighting mostly right, which is fine, but it's not a real IDE.
Let me go over the domains one at a time:
PHP: Syntax highlighting- Yes. Code completion- Flaky (sometimes incorrect)
jQuery: Not really acceptable
MySQL: No support
FTP: Yes, Dreamweaver will transfer files over FTP.
Instead, I'd recommend Netbeans, which I've just switched to, and is much better (and cheaper (it's free!)) than Dreamweaver.
I personally use and highly recommend Eclipse with WTP (web tools) and PDT (PHP Development tools) for PHP, js and css development.
Also it has lot of plugins to work with MySQL databases, apache servers, SVN repositories or whatever you could need...
To install it I recommend using an all-in-one package from here