title: PHP \MongoDB\Driver\BulkWrite can't delete _id.$oid Object
body: <p>I have a script removing Mongo records on PHP7 \MongoDB\Driver as this</p>
  
  <pre><code>$db = new \MongoDB\Driver\Manager(".......");
  $bulk = new \MongoDB\Driver\BulkWrite;
  $bulk-&gt;delete(["_id":"5887e6fda69ca3797f74a4fd"], ['limit' =&gt; 1]);
  $writeConcern = new \MongoDB\Driver\WriteConcern(\MongoDB\Driver\WriteConcern::MAJORITY, 1000);
  $result = $db-&gt;executeBulkWrite('theplace.here', $bulk, $writeConcern);
  </code></pre>
  
  <p>I also tried</p>
  
  <pre><code>...
  $bulk-&gt;delete(["_id.$oid":"5887e6fda69ca3797f74a4fd"], ['limit' =&gt; 1]);
  ...
  </code></pre>
  
  <p>This works for any field I send, it does delete... it just doesn't work when I want to remove an _id _id.$oid, like if it was ignoring without throwing errors.</p>
  
  <p>Any help really appreciated.</p>