Ah, but does it run? If it does then it's Dreamweaver's problem!
I think Dreamweaver just does anything between < and > as blue.
If you want syntax highlighting for your PHP (and HTML, and Javascript, and VBScript, and Perl, and SQL, and C, and Java) I use HTML-Kit, www.chami.com/html-kit/. It's not WYSIWYG, and its workspace rendering feels slow, but it works very nicely (except on my Win95 machine for some ungodly reason) and spectacularly extensible.