How can I use PHP to print a view in the content area of a page?
As a starting point I would have the function return the view rather than attempting to print it. Try:

 $content['view'][] = views_embed_view('profile_show_user_interests','show_interests_own', $participant-&gt;uid);


and then render it in the page at the proper place. (views_get_view might be better in this context.)