You have to have a .php page open and you have to have a site defined in Dreamweaver with the .php page you have opened saved into the site folder.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.