I have noticed that often times PhpEd will show an asterisk(*) at the top of the screen next to the currently active file name, indicating that the file has changed since it was last saved, even though I have not changed anything. This has been happening a lot, and whenever I notice it, I just hit undo. Then the * disappears, but none of the code changes. It just now happened again, I hit undo, the * disappeared, and then I wondered what would happen if I hit redo. So I tried doing a redo and several lines of code were deleted from the top of the file.

You need to turn off "Optimal Fill" in the settings: Tools menu, Settings... Editor Settings, uncheck Optimal Fill

I asked pretty much the same thing not too long ago

See this thread --> possible-bug-ide-thinks-file-has-changed-t3607.html

I'd also point out to
undo-broken-b5022-t3471.html
and of course we have FAQ on this topic: http://www.nusphere.com/kb/technicalfaq/faq_wrk_with_phped.htm (see p.5)

Thanks that fixed the problem. I had 'keep trailing blanks' disabled, but I don't mind enabling it. You should really disable these features that are causing serious prpbs. Thanks for the workaround.