Description:
------------
---
From manual page: http://www.php.net/mongodb-driver-manager.executequery
---
using the current version of mongodb driver,it has a bug in building a filter for a query when use '$or' operator to the same field.
there is field named "foo" ,not every docs has this field. I want to search a list contain the docs that not has field "foo" or "foo" is equal to "value" . I shoud build a filter such as below:
['$or'=>[
'foo'=>['$exists'=>false],
'foo'=>['$eq'=>"value"]
]]
so the key has named twitce,we can't use array to define a filter 

Expected result:
----------------
may be
['$or'=>[
['foo',['$exists'=>false]],
['foo',['$eq'=>"value"]]
]]
or
{ $or : [ { foo : { $exists: false } }, { foo : value } ] }