I guess now I know why it didn´t worked last time. Recently, I had a similar problem recently and as you sayed my php-page was presented within ML, but all the options which were programmed in php were not available. In the html file I used recently I set some text-form fields on readonly and added php-variables which should be presented instead of type-in-text-form field, and instead the variables values only the php-code was presented (the <?php ...>). So I guess that the problem simply was that php-code was not parsed if you just click a file into ML by using the html-item (i.e. by not calling php-files by an url), and then of course all other links which directed to another location in the same php-file were also "broken". Rookie-mistake made by me, sorry.

Best,
Tom