note 7928 deleted from mysql_insert_id by danbeck

This seems to have just appeared in PHP4 pl2 though perhaps it is library dependent. Anyways, contrary to the docs, with PHP4 running mysql_insert_id($result) always gives an invalid link identifier warning when passed the result from the previous query. If you leave the link identifier out then it works fine. This is contrary to what the docs suggest - they say both should be fine and really, for safety I think you should always expressly be passing a link identifier.