Doctrine ODM，MongoDB，Symfony2 - 插入文档会创建两个数据库条目，应该创建一个

Question

I'm new to Symfony 2 with Mongo (I've used Symfony before and I used MongoDB before, just not them together).

I have this code in Symfony 2:

$dm = $this->container->get('doctrine_mongodb');
$manager = $dm->getManager();
$pain = new Pain();
$pain->setScale(5);
$pain->setDateStart(new \DateTime());    
$manager->persist($pain);
$manager->flush();

Pretty basic Symfony stuff. But running this code once creates two database entries like this:

> db.Resources.find();
{ "_id" : ObjectId("5276842640b59ece04000000"), "scale" : 5, "dateStart" : ISODate("2013-11-03T17:13:10Z"), "type" : "pain" }
{ "_id" : ObjectId("5276842740b59ecd04000004"), "scale" : 5, "dateStart" : ISODate("2013-11-03T17:13:11Z"), "type" : "pain" }

Here is my config.yml:

doctrine_mongodb:
connections:
    default:
        server: mongodb://localhost:27017
        options: {}
default_database: znmj
document_managers:
    default:
        auto_mapping: true

And here's the Pain class:

/**
 * @MongoDB\Document(collection="Resources")
 */
class Pain
{
/**
 * @MongoDB\Id(strategy="auto")
 */
protected $id;  

/**
 * @var integer
 * @MongoDB\Int
 */
protected $scale;

    // getters and setters below
}

I really can't figure out how to handle this issue or debug it. I can get 0 or 2 entries in the database. I Googled a lot for this, and couldn't find anything even remotely related.

Any ideas on what may be causing the problem?

UPDATE: And of course the culprit was <link rel="shortcut icon" href=""> This is a great lesson in debugging.