Count Documents
On this page
Overview
In this guide, you can learn how to use the MongoDB PHP Library to retrieve an accurate and estimated count of the number of documents in a collection. The following methods count documents in a collection:
MongoDB\Collection::countDocuments()
: Returns the exact number of documents that match a query filter or that exist in a collectionMongoDB\Collection::estimatedDocumentCount()
: Returns the estimated number of documents in a collection
Sample Data
The examples in this guide use the companies
collection in the sample_training
database from the Atlas sample datasets. To access this collection
from your PHP application, instantiate a MongoDB\Client
that connects to an Atlas cluster
and assign the following value to your $collection
variable:
$collection = $client->sample_training->companies;
To learn how to create a free MongoDB Atlas cluster and load the sample datasets, see the Get Started with Atlas guide.
Retrieve an Accurate Count
Use the MongoDB\Collection::countDocuments()
method to count the number of documents
in a collection. To count the number of documents that match specific search criteria,
pass a query filter to the countDocuments()
method.
To learn more about specifying a query, see the Specify a Query guide.
Count All Documents
To return a count of all documents in the collection, pass an empty query filter array to
the countDocuments()
method, as shown in the following example:
$result = $collection->countDocuments([]); echo 'Number of documents: ', $result;
Number of documents: 9500
Count Specific Documents
To return a count of documents that match specific search criteria, pass a query
filter to the countDocuments()
method.
The following example counts the number of documents in which the value of the
founded_year
field is 2010
:
$result = $collection->countDocuments(['founded_year' => 2010]); echo 'Number of companies founded in 2010: ', $result;
Number of companies founded in 2010: 33
Customize Count Behavior
You can modify the behavior of the countDocuments()
method by
passing an array that specifies option values. The following table
describes some options you can set to customize the count operation:
Option | Description |
---|---|
collation | The collation to use for the operation. Type: array|object |
hint | The index to use for the operation. Type: string|array|object |
comment | The comment to attach to the operation. Type: any valid BSON type |
limit | The maximum number of documents to count. This value must be a positive integer. Type: integer |
maxTimeMS | The maximum amount of time in milliseconds that the operation can run. Type: integer |
skip | The number of documents to skip before counting documents. Type: integer |
readPreference | The read preference to use for the operation. To learn more, see
Read Preference in the Server manual. Type: MongoDB\Driver\ReadPreference |
The following example uses the countDocuments()
method to count the number of
documents in which the number_of_employees
field has the value 50
and instructs the
operation to count a maximum of 100
results:
$result = $collection->countDocuments( ['number_of_employees' => 50], ['limit' => 100] ); echo 'Number of companies with 50 employees: ', $result;
Number of companies with 50 employees: 100
Retrieve an Estimated Count
You can retrieve an estimate of the number of documents in a collection by calling
the MongoDB\Collection::estimatedDocumentCount()
method. The method estimates
the amount of documents based on collection metadata, which might be faster than
performing an accurate count.
The following example estimates the number of documents in a collection:
$result = $collection->estimatedDocumentCount(); echo 'Estimated number of documents: ', $result;
Estimated number of documents: 9500
Customize Estimated Count Behavior
You can modify the behavior of the estimatedDocumentCount()
method
by passing an array that specifies option values as a parameter. The
following table describes the options you can set in the array:
Option | Description |
---|---|
comment | The comment to attach to the operation. Type: any valid BSON type |
maxTimeMS | The maximum amount of time in milliseconds that the operation can run. Type: integer |
readConcern | The read concern to use for the operation. To learn more, see
Read Concern in the Server manual. Type: MongoDB\Driver\ReadConcern |
readPreference | The read preference to use for the operation. To learn more, see
Read Preference in the Server manual. Type: MongoDB\Driver\ReadPreference |
session | The client session to associate with the operation. Type: MongoDB\Driver\Session |
The following example uses the estimatedDocumentCount()
method to return an
estimate of the number of documents in the collection and sets a timeout of
1000
milliseconds on the operation:
$result = $collection->estimatedDocumentCount(['maxTimeMS' => 1000]); echo 'Estimated number of documents: ', $result;
Estimated number of documents: 9500
API Documentation
To learn more about any of the methods or types discussed in this guide, see the following API documentation: