通过自动'_id'字段搜索MongoDB，这不可能吗？

Question

I am trying to query MongoDB and find the row which has a specific '_id' but I can not do that. When I write for example:

$r = $cursor->getNext(); 

and debug, I find the value of $r['_id'] is empty. Not null, but empty! Any idea why this happens and how to avoid it? Using PHP

Update:

I was able to retrieve the '_id' by $cursor->key() but still I can't query and I wonder why the reason behind that!

Answer 1

I was able to retrieve the '_id' by $cursor->key() but still I can't query and I wonder why the reason behind that!