Ok, I personally use Namo Web Editor and it is very simple to create a PHP file and you can edit it like a normal document. Now...after saying that, you will see (or at least in my web editor) I will see a script tag with a question mark telling me what php tags are embedded in the php page. I presume it is the same in Dreamweaver but as I haven't used it for a while, I wouldn't know....
I create my php pages first in notepad and then save them with a .php extension and then drag them over into my web editor and there I use it to add different things to it. My document is surrounded in <html> tags with small bits of php code in it...
Now...for php I don't know if this is what you are asking but to make a pure php page the tages should be
<? you stuff here ?>
If you want to have a login script I would download this one that I got it is called vAuthenticate...it is free and I just modified it to fit with my MySQL database and so that I could customize my own login pages...
You can download it here:
http://www.beanbug.net/vScripts.phpHope this helps...
ADAM