Judging by your url, I have one comment about it. The url makes it seem as if your editing something on the page, I would go back to using the POST request or implement your own CRSF protection on the GET request if your page allows for editing of anything important. VB's CSRF does not cover get requests only post requests.
1.
PHP Code:
if(empty($_REQUEST['uid'])){
//there was no uid sent to the form
}
2. when your finished with the database.