mongodb $nin not work in php

Question

Current Code:

$doc = array('ooxx' => array(1,2,3,4,5));

datamodel()->insert($doc);

$doc2 = array('ooxx' => array(6,7,8,9));
datamodel()->insert($doc2);

$macher = array('ooxx'=>array('$exists' => true), 'ooxx' => array('$nin'=>array(6)));
$res = datamodel()->findOne($macher);
print_r($res);

When I replace the $macher with bellow, it does work well, why? is this a bug of mongodb?

$macher = array( 'ooxx' => array('$nin'=>array(6)), 'ooxx'=>array('$exists' => true));

Answer 1

It doesn't work because the keys have the same name and one overwrites the other. So the "keys" need to be unique.

If you have two conditions for the same key you use the $and operator which takes an array of arguments:

$matcher = array(
    '$and' => array( 
        array( 'ooxx' => array( '$nin' => array(6) ) ),
        array( 'ooxx' => array( '$exists' => true ) )
    )
)

Or for the JSON minded:

{
    "$and": [
        { "ooxx": { "$nin": [6] } },
        { "ooxx": { "$exists": true } }
    ]
}

Which is a valid structure where what you are writing is not.