How to convert string to ObjectId in native php mongodb driver?

I am using mongodb driver in php environment (frameworkign framework) and I need to convert id string to ObjectId in order to use it in my update request, how can I do that? I've tried the following code but it doesn't work.

     $collection->update(array('_id'=> $NewDeviceArray["myid"], $newdata);

      

        
        
        
      

    

I also tried a suggestion on google to convert string to objectid.but but that also failed.

     $convertedid= new MongoId($NewDeviceArray["myid"]);
     $collection->update(array('_id'=> $convertedid, $newdata);

      

        
        
        
      

    

Any hints would be much appreciated.

Update

after fixing the syntax error, $ collection-> update (array ('_ id' => $ conversionid), $ newdata);

Now it works !!!