Description:
------------
I execute the following query:

INSERT INTO test VALUES (NULL,'key','value') ON DUPLICATE KEY UPDATE v='value';

key exists and value of v column is the same as new value in UPDATE clause.
I call $id=mysql_insert_id(); and expect that $id is id of existing row (id is INT NOT NULL PRIMARY KEY AUTO_INCREMENT column) but $id contains another value.

MySQL version is 5.0.51a

Reproduce code:
---------------
<?php
/* MySQL table definition
CREATE TABLE test
(
    id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
    k VARCHAR(10) NOT NULL UNIQUE,
    v VARCHAR(10) NOT NULL
);
*/

$db_host='localhost'; //database host
$db_user=''; //database user
$db_pass=''; //database password
$db_name='test'; //database name

mysql_connect($db_host,$db_user,$db_pass); //connect to database
mysql_query("USE $db_name"); //select database
mysql_query('TRUNCATE test'); //clear test table
mysql_query('INSERT INTO test VALUES (NULL,\'key\',\'value\')');
mysql_query('INSERT INTO test VALUES (NULL,\'key\',\'value\') ON DUPLICATE KEY UPDATE v=\'value\'');
$id=mysql_insert_id();
mysql_close();
echo("Expected id is 1, id is $id\n");
?>


Expected result:
----------------
I expect $id to be 1

Actual result:
--------------
$id is 2