Selectively post form to different pages, based on form result?

Selectively post form to different pages, based on form result?

Say I have a simple form on a page called photo/delete.php. This form
deletes an image specified by the user. All it is, is this:
<form action="?" method="post">
<input type="checkbox" name="confirmDelete" value="confirm" />
<input type="submit" value="delete" />
</form>
So, this form contains a confirmation check box that must be ticked to
ensure the image is deleted. How can I dynamically choose what page to
POST this form to, based on its contents?
For example, if the checkbox is not checked, yet the submit button is
clicked, I'd like to stay on the same photo/delete.php page and display an
error, since its possible they really do want to delete the image and
simply forgot to tick the box.
But otherwise, if everything is successful and the checkbox is ticked, I'd
like to POST it to another page, say home.php since it makes no sense to
stay on the same page of a just-deleted image.
How can I implement this?