mongodb - PHP 5.2.13 MongoCursorException 'duplicate key error index' -

i'm getting duplicate _ids when inserting documents our mongo database. intermittent problem happens under load (is reproducable test scripts).

here's test code don't think i'm trying double-insert same object (i know php mongo driver adds _id field):

// insert job $job = array(     'type'      =>  'cleanup',     'meta'      =>  'cleaning data',     'user_id'   =>  new mongoid($user_id),     'created'   =>  time(),     'status'    =>  'pending' ); $this->db->job->insert($job, array('safe' => true));      // <-- failz here 

i went on frenzy , installed latest stable (1.1.4) mongo driver no avail. isn't under heavy load. we're doing maybe 5 req/s on 1 server, 16m rec/s limit inc value isn't issue.

any ideas appreciated. i'm hoping somewhere has used mongo php , inserted more 5 docs/s , had issue ;).

-edit-
on centos 5.4 x86_64, linux 2.6.18-164.el5xen, apache worker 2.2.15, php 5.2.13, mongodb 1.8.1

-edit2-
noted in comments, i'm using latest version of pecl driver of (1.2.0) , problem still happening.

-edit3-
forgot post exact error:

uncaught exception 'mongocursorexception' message 'e11000 duplicate key error index: hannibal.job.$_id_ dup key 

there different solution (the preform/worker mpm didn't in case, running prefork default anyway).

the issue insert array passed reference, , modified php mongodb library include id. need clear id.

so imagine following code:

$atoinsert = array('field'=>$val1); $collection->insert($atoinsert);   << have '_id' added $atoinsert['field'] = $val2 $collection->insert($atoinsert);  << fail above error 

why? happens library is:

$atoinsert = array('field'=>$val1); $collection->insert($atoinsert);  // $atoinsert has '_id' added php mongodb library // therefore $atoinsert = array('field'=>$val1, '_id'=>mongoid() );  $atoinsert['field'] = $val2 // therefore $atoinsert = array('field'=>$val2, '_id'=>mongoid() );  $collection->insert($atoinsert); // not add '_id' exists. fail. 

solution reinitialise array

$atoinsert = array('field'=>$val1); $collection->insert($atoinsert); $atoinsert = array('field'=>$val2); $collection->insert($atoinsert); 

or unset id

$atoinsert = array('field'=>$val1); $collection->insert($atoinsert); unset($atoinsert['_id']); $atoinsert['field'] = $val2 $collection->insert($atoinsert);  << work