I just did a fresh install of Notepad++. While Notepad++ was closed, I opened up shortcuts.xml from the C://Users/User/AppData/Roaming/Notepad++ folder (Windows7) and changed the following line:
<Command name="Launch in Firefox" Ctrl="yes" Alt="yes" Shift="yes" Key="88">firefox "http://localhost/redirect.php?file=$(FULL_CURRENT_PATH)"</Command>
This change was suggested in an answer to another StackOverflow question: Configuring Notepad++ to run php on localhost?
When I opened Notepad++ after the change, there were no items in the "Run" dropdown menu, and shortcuts.xml was stripped to bare bones as follows:
<NotepadPlus>
<InternalCommands />
<Macros />
<UserDefinedCommands />
<PluginCommands />
<ScintillaKeys />
</NotepadPlus>
The reason I did a fresh install was that I already ran into this problem. Although it might seem that it would be a simple matter to just copy and paste the original file, every time I restart Notepad++, the shortcuts.xml file gets wiped out. The only way that I have found to restore shortcuts.xml is by a fresh install, and it looks like there is no way to edit it without it getting wiped out.
I also tried editing the shortcuts.xml in the C://Program Files (x86)/Notepad++ folder. Although the XML file there didn't get wiped out, any changes made there seemed to be completely ignored by Notepad++. According to the the answer in the link I posted above, that is also the wrong file to edit.
I tried Googling the problem, but I didn't find anything.
UPDATE:
Without doing anything except for changing 'Firefox' to 'Mozilla,' it didn't wipe out the file, but as soon as I made the other changes to the line, it wiped it out again. Once it's wiped out, I haven't been able to restore it without a reinstall.
This seems to indicate that it depends on what edits are made. However, I've seen that other people have successfully launched PHP files in localhost from Notepad++, so it looks like this version is a little buggy in some respects.