group by date in laravel mongodb - mongodb

Question

I'm using mongo and laravel.
I'm getting data in periods of time, usually 30 days. I want to group the data by day. I've tried $project $dayOfMonth and group by day but it grouping them in order of days in month and I want to be ordered in days in the period.
is there a way?
[
'$match' => [
"created_at" => [
'$gte' => new \MongoDB\BSON\UTCDateTime($thisMonth),
]
],
],
[
'$project' => [
'day' => [
'$dayOfMonth' => [
'date' => '$created_at',
]
],
]
],
[
'$group' => [
'_id' => '$day',
'count' => ['$sum' => 1],
],
],
sample:
{#940
flag::STD_PROP_LIST: false
flag::ARRAY_AS_PROPS: true
iteratorClass: "ArrayIterator"
storage: array:16 [
"_id" => ObjectId {#933
+"oid": "5b2ff00e35826377be16ff82"
}
"orderNumber" => "10000"
"userName" => "dGFraHRlLTkwMDQ2NDcyOJRbugaZlHWdMR+nCNzaUfY="
"updated_at" => UTCDateTime {#938
+"milliseconds": "1529868539000"
}
"created_at" => UTCDateTime {#939
+"milliseconds": "1529868302000"
}
]
}

Answer 1

You can use $dateFromString to converts a date object to a string according to a your desired format.
[ "$match" => [
"created_at" => [ '$gte' => new \MongoDB\BSON\UTCDateTime($thisMonth) ]
]],
[ "$group" => [
"_id" => [ "$dateToString" => [ "format" => "%Y-%m-%d", "date" => "$created_at" ] ],
"count" => [ "$sum" => 1 ]
]]