When you reply, scroll down to the additional; options section. You can add attachments to your reply here.
First compress the php file into a zip archive, when you reply, you can attach the zip archive to your reply.
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.