I Googled this question and found this post. I was able to get the code highlighting for PHP and HTML and other code as well. I resolved it by doing a few things;
Open the XML document named "MMDocumentTypes.xml" located in "C:\Program Files\Macromedia\Dreamweaver MX\Configuration\DocumentTypes"
Find the following code;
<documenttype id="PHP_MySQL" servermodel="PHP MySQL" internaltype="Dynamic" winfileextension="php,php3" macfileextension="php,php3" file="Default.php">
<TITLE>
<MMString:loadString id="mmdocumenttypes_14" />
</TITLE>
<description>
<MMString:loadString id="mmdocumenttypes_15" />
</description>
</documenttype>
Copy the above code and copy [Ctrl + C]
Go o the end of the document [Ctrl + End] and Paste [Ctrl + V]
Change the following code;
winfileextension="php,php3" macfileextension="php,php3"
to
winfileextension="tpl" macfileextension="tpl"
- Change the following code;
<MMString:loadString id="mmdocumenttypes_14" />
and
<MMString:loadString id="mmdocumenttypes_15" />
to
<MMString:loadString id="mmdocumenttypes_64" />
and
<MMString:loadString id="mmdocumenttypes_65" />
Note: The above two numbers (64 & 65) should be the next two largest numbers in the XML document.
Save and close the file.
Go to "Edit / Preferences" in Dreamweaver, click "File Types/Editors" and add the extension .tpl to the Extensions list and add Dreamweaver as the Editor