Ohne Cache und ohne Gewehr:
$conn = mysql_connect("localhost", '','') or die("Keine DB Verbindung");
mysql_select_db("myweb", $conn) or die(mysql_error());
$id = insert_user('hh22', 'Horst Haselhuhn');
print $id;
function insert_user($user_id, $user_name){
$st = "INSERT INTO user(user_id, user_name)VALUES('$user_id','$user_name')";
$st .= "ON DUPLICATE KEY UPDATE id = LAST_INSERT_ID(id)";
mysql_query($st);
$res = mysql_query("SELECT LAST_INSERT_ID() as myid");
$id = mysql_fetch_assoc($res);
return $id['myid'];
}
Horst Kopfschuss ;)