Hello There is no possibility to define own open dialog filter independent of the extensions defined in highlighters. You can hide highlighters you don't use in menu Settings / Highlighter settings. Uncheck highlighters in list. Highlighters will stay available, syntax will be highlightd when you open file, but disappears from new file list, open dialog filters e.t.c.
You can add PHP extensions to your HTML highlighter (menu settings / Highlighters / HTML), but this solution isn't ideal. -- <http://forum.pspad.com/read.php?2,60000,60005> PSPad freeware editor http://www.pspad.com
