You cannot strip a certain list of tags with PHP’s strip_tags() function, you can only strip ‘all but’ tags.
So in order to do so, you’ll need to use regular expressions to do it swiftly:
$strip_list = array('strong', 'p', 'div');
foreach ($strip_list as $tag)
{
$string = preg_replace('/<\/?' . $tag . '(.|\s)*?>/', '', $html);
}
Job done.