FlashDevelop is one of the most preferred editors for the flash development. I've been also using it last few years. I found it helpful for writing JavaScript, HTML, CSS and PHP code as well. I just took a big project with over 1000 php files and it is a little bit difficult to open the right file, even by using the Project panel. That's why I decided to invest time in solving this task and found that I can write my own C# script and run it.