The first portable app that I ever used is HAPEdit (HTML, ASP, PHP Editor). This is freeware written by someone in France, but it is not open source.
I have no affiliation to this product other than the fact that I use it. It supports more than just HTML, ASP, and PHP. It also support javascript files, css, more. This really is free, without adware, malware, nag screens, etc. I've used it for more than a year and it continues to be my default php site editor.
I was thinking that this is something that you may wish to add to the editor section of the site. You can find the application at:
Also, try PSPad.
http://www.pspad.com/
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R McCue
"If you're not part of the solution, you're part of the precipitate."