[SimonP]

mysql_query("LOCK TABLES mintabell WRITE") or die("error");
$result = mysql_query("SELECT MAX(ID) AS LAST_ID FROM mintabell") or die("error");
$result = mysql_fetch_array($result);
echo "Last id = " . $result[LAST_ID];
mysql_query("UNLOCK TABLES");

Ovanstånde ska vara säkert.