I just checked in some code to allow editing of HTML comments, PHP and Processing Instructions in BlueGriffon. A few limitations :

  • file pickers don't allow to select PHP files yet, that will be handled by another bug
  • that code adds support for PHP inside HTML, not for HTML inside PHP...
  • copying and pasting of a chunk containing a comment or processing instruction (including PHP) in Wysiwyg view does not work yet