I've been coding PHP/MySQL/HTML/Javascript...blah blah for about 15 years now. The real important thing to remember is that true PHP coding professionals need the proper tools, along with support of all the other languages that you employ.
Using that logic, Dreamweaver becomes a very bad choice for PHP programmers. There is no real-time syntax checking, nor is there any kind og PHP bookmarks/breakpoints that can run in real time. There is no debugger either. However, it's pretty good for plain ol HTML/CSS stuff. It's quite overpriced compared to the high quality free options.
Coda is also way overpriced and lack quite a few important features in my opinion. No debugging, no real syntax checker until you actually save and then you get some light notifications. It is a decent text editor and allows splitting of screens. But it nowhere near justifies it's $100 price tag. Perhaps $40 or perhaps $50 would be more in line.
Smultron, which is free is outstanding, but it's limited in project control. It's also pretty much a text editor, but better than most. It's about the same as BBEdit.
I've also used Zend, which touts itself as the PHP leader, but it's editor can't even do word wrap. It, like Dreamweaver, is quite expensive for what you get.
There are actually two great solutions that are free, offer complete support for all web languages, have debugging and offer real-time syntax checking with database interfacing. NetBeans supports ALL languages including Java if you are so inclined. Their PHP support is excellent, along with almost anything else. The Aptana Studio version 1.5, if you can still find it, is also excellent. The newer Aptana Studio version 2 and above, only uses PDT and thus is a big step backwards.
Bottom line, try NetBeans (Netbeans.org) and I think you'll be VERY happy.