passing NULL to mysql procedure

I have the following mysql procedure:

CREATE PROCEDURE db.processEvent( IN eventId INT , IN creatorId INT , IN typeId INT , IN eventName VARCHAR( 60 ) , IN startDateTime DATETIME , IN endDateTime DATETIME , IN validStartTime TIME , IN validEndTime TIME )
BEGIN
    INSERT INTO tbl_event
    VALUES
    (
        eventId , creatorId , typeId , eventName , startDateTime , endDateTime , validStartTime , validEndTime
    )
    ON DUPLICATE KEY UPDATE
        creator_user_id = creatorID ,
        event_type_id = typeId ,
        event_name = eventName ,
        start_date = startDateTime ,
        end_date = endDateTime ,
        valid_time_start = validStartTime ,
        valid_time_end = validEndTime
    ;
END;

ON first run it does the correct thing and create a new record as I pass NULL into eventId. It also updates when I pass an id in for eventId (I am assuming it updates correctly at this stage).

However... If I go to create a new record by pass NULL in to eventId the initial record is updated.

I have tried adding:

    IF eventId != 0 OR eventId IS NOT NULL THEN
        set eID = eventId;
    END IF;

and using eID in the values list but to no avail.

Any clues would be a great help.

Thanks peeps.

==========================

Requested Info:

table strcuture:

CREATE TABLE `tbl_event` (
`event_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`creator_user_id` int(10) unsigned NOT NULL,
`event_type_id` int(11) NOT NULL,
`event_name` varchar(60) DEFAULT NULL,
`start_date` datetime DEFAULT NULL,
`end_date` datetime DEFAULT NULL,
`valid_time_start` time DEFAULT NULL,
`valid_time_end` time DEFAULT NULL,
PRIMARY KEY (`event_id`,`creator_user_id`),
UNIQUE KEY `event_id_UNIQUE` (`event_id`),
UNIQUE KEY `creator_user_id_UNIQUE` (`creator_user_id`),
KEY `fk_tbl_event_tbl_cm_profile1` (`creator_user_id`),
KEY `fk_tbl_event_tbl_event_type1` (`event_type_id`),
CONSTRAINT `fk_tbl_event_tbl_cm_profile1` FOREIGN KEY (`creator_user_id`) REFERENCES `tbl_cm_user_profile` (`cm_user_id`),
CONSTRAINT `fk_tbl_event_tbl_event_type1` FOREIGN KEY (`event_type_id`) REFERENCES `tbl_event_type` (`event_type_id`)
) ENGINE=InnoDB

called via php:pdo like so:

$db     = \lib\DBObj::getInstance( DBUSE );
$prEvnt = $db->prepare( 'CALL processEvent(:id , :creator , :type , :name , :startDate , :endDate , :startTime , :endTime );' );

$prEvnt->bindValue( ':id' , $event_id , \PDO::PARAM_INT || \PDO::PARAM_NULL );
$prEvnt->bindValue( ':creator' , $usr->getId() , \PDO::PARAM_INT );
$prEvnt->bindValue( ':type' , $event_type , \PDO::PARAM_INT );
$prEvnt->bindValue( ':name' , $event_name , \PDO::PARAM_INT );
$prEvnt->bindValue( ':startDate' , $start_date , \PDO::PARAM_STR );
$prEvnt->bindValue( ':e开发者_如何学GondDate' , $end_date , \PDO::PARAM_STR );
$prEvnt->bindValue( ':startTime' , $start_time , \PDO::PARAM_STR || \PDO::PARAM_NULL );
$prEvnt->bindValue( ':endTime' , $end_time , \PDO::PARAM_STR || \PDO::PARAM_NULL );
$prEvnt->execute();

Oh Dear - I just noticed the primary key and the references!!!

Removed creator_id from primary key and the identifying refernce to event type - all is now sweet...