How to pass an empty php variable in mongodb query

Question

I want to create a dynamic mongodb query which insert each part of it's aggregation if the condition is true else don't inject that part.

For example I want to check if the time is between 1AM till 8AM If yes then pass in the defined array to the mongodb query else pass nothing.

if ($this->Not_in_1_8 == true) {
    $this->N_IN_1_8 = array('dont_show_between_1_n_8' => array('$ne' => true));
}else {
    $this->N_IN_1_8 = null;
}
$MidnightCheck = $this->N_IN_1_8;
$this->campaign = Bcamp::raw(function ($collection) use ($seat_category_list, $banner_size, $seat_filter_list, $gold_network, $MidnightCheck) {
    return $collection->aggregate([
        [
            '$match' => [
                '$and' => [
                    ["targets.cats" => [
                        '$in' => $seat_category_list
                        ]
                    ],
                    ['banners.' . $banner_size => [
                        '$exists' => true
                        ]
                    ],
                    ['href' => [
                        '$nin' => $seat_filter_list
                        ]
                    ],
                    ['targets.gold_network' => [
                        '$eq' => $gold_network
                        ]
                    ],
                    ['status' => [
                        '$ne' => "Low_Budget"
                        ]
                    ],
                    ['daily_budget_status' => [
                        '$ne' => "Low_Budget"
                        ]
                    ],
                    $MidnightCheck
                ]
            ]
        ],
        [
            '$project' => [
                'ab' => [
                    '$cmp' => [
                        '$budget', '$click_cost'
                    ]
                ]
            ]
        ],
        [
            '$match' => [
                'ab' => [
                    '$lt' => 1
                ]
            ]
        ]

    ]);
});

But In this example It will inject null into query and makes it wrong and I catch error : bad query: BadValue: $or/$and/$nor entries need to be full objects

I have changed it to $this->N_IN_1_8 = ''; still no success.

All I need a neutral variable or condition to pass in which does not affect on query if the condition if false. Any Idea?

FYI : I'm using Laravel 5.3 framework with jenssegers/laravel-mongodb package for working with mongodb

Answer 1

Prefering to keep the code structure as is i.e. when a pre-built array is not used in the condition code, you may keep $MidnightCheck as null and wrap the array with array_filter:

return $collection->aggregate([
[
    '$match' => [
        '$and' => array_filter([
            ["targets.cats" => ['$in' => $seat_category_list]],
            ['banners.' . $banner_size => ['$exists' => true]],
            ['href' => ['$nin' => $seat_filter_list]],
            ['targets.gold_network' => ['$eq' => $gold_network]],
            ['status' => ['$ne' => "Low_Budget"]],
            ['daily_budget_status' => ['$ne' => "Low_Budget"]],
            $MidnightCheck
        ])
    ]
// ...

Calling array_filter without a second argument will filter out all false values from the array, causing the unwanted $MidnightCheck will be gone.

What I think might be clearer would be to pre-prepare the conditions in the callback:

$conditions = [
    ["targets.cats" => ['$in' => $seat_category_list]],
    ['banners.' . $banner_size => ['$exists' => true]],
    ['href' => ['$nin' => $seat_filter_list]],
    ['targets.gold_network' => ['$eq' => $gold_network]],
    ['status' => ['$ne' => "Low_Budget"]],
    ['daily_budget_status' => ['$ne' => "Low_Budget"]],
];
if ($MidnighCheck) {
    $conditions[] = $MidnightCheck;
}
return $collection->aggregate([
    ['$match' => [ '$and' => $conditions ],]
])