C'est bon j'ai fais ca, ca marche : if (isset($_GET['supprimer_question']))
{
mysql_query("DELETE FROM quizz WHERE ID = ".$_GET['supprimer_question']); // Requete SQL pour supprimer la question voulue
$totalquestion = mysql_query("SELECT COUNT(ID) AS total FROM quizz");
$val = mysql_fetch_array($totalquestion);
$derniere_question = $val['total']+1;
mysql_query("UPDATE quizz SET ID = '".$_GET['supprimer_question']."' WHERE ID = ".$derniere_question);
}