I would submit to an entirely different page instead of to php_self?. And then put a redirect on the page you submitted to, to redirect you back to the submission page or whatever page you want to go to. Example:
FORM PAGE
<form>
<form action="post.php" method="POST">
<input stuff goes here>
</form>
PAGE THAT CONNECTS TO DATABASE
-do all of your database inserts
then put this at the top of your header stuff,
header ("location: http://some_url");