[Plugin: TinyMCE Advanced] converts and deletes html entities

When tinymce-advanced is active, I cannot insert code snippets in my post, even when I use html entities.
the line & lt; ?php do_something(); ?& gt; will be converted to <?php do_something(); ?> on the first save. When I save the post a second time, it is stripped from the post because it has become ‘real code’.
My request: please leave html entities as is!

note I had to insert spaces because this editor even double converts html entities.