=========================
Execute Database Commands
=========================

.. default-domain:: mongodb

.. contents:: On this page
   :local:
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   :depth: 2
   :class: singlecol

Overview
--------

The |php-library| provides :ref:`helper methods <database-methods>`
for common :manual:`database commands </reference/command>`. In
addition, the |php-library| provides the
:phpmethod:`MongoDB\\Database::command` method to run database commands
with PHP that do not have helper methods.

Execute Database Commands
-------------------------

Basic Command
~~~~~~~~~~~~~

To execute a command on a :program:`mongod` instance, use the
:phpmethod:`MongoDB\\Database::command` method. For instance, the
following operation uses the :dbcommand:`geoNear` HERE command to search for
the three closest documents to longitude ``-74`` and latitude ``40`` in
the ``restos`` collection in the ``example`` database:

:readmode:`secondary`

.. code-block:: php

   <?php

   $database = (new MongoDB\Client)->example;

   $results = $database->command(
       [
           'geoNear' => 'restos',
           'near' => [
               'type' => 'Point',
               'coordinates' => [-74.0, 40.0]
           ],
           'spherical' => 'true',
           'num' => 3
       ]
   );

   var_dump($results);

The output would resemble::
  
  object(MongoDB\Driver\Cursor)#10 (2) {
    ["cursor"]=>
    array(17) {
      ["stamp"]=>
      int(0)
      ["is_command"]=>
      bool(true)
      ["sent"]=>
      bool(true)
      ["done"]=>
      bool(false)
      ["end_of_event"]=>
      bool(false)
      ["in_exhaust"]=>
      bool(false)
      ["has_fields"]=>
      bool(false)
      ["query"]=>
      object(stdClass)#3 (4) {
        ["geoNear"]=>
        string(6) "restos"
        ["near"]=>
        object(stdClass)#9 (2) {
          ["type"]=>
          string(5) "Point"
          ["coordinates"]=>
          array(2) {
            [0]=>
            float(-74)
            [1]=>
            float(40)
          }
        }
        ["spherical"]=>
        string(4) "true"
        ["num"]=>
        int(3)
      }
      ["fields"]=>
      object(stdClass)#8 (0) {
      }
      ["read_preference"]=>
      array(2) {
        ["mode"]=>
        int(1)
        ["tags"]=>
        array(0) {
        }
      }
      ["flags"]=>
      int(0)
      ["skip"]=>
      int(0)
      ["limit"]=>
      int(1)
      ["count"]=>
      int(1)
      ["batch_size"]=>
      int(0)
      ["ns"]=>
      string(12) "example.$cmd"
      ["current_doc"]=>
      object(stdClass)#24 (4) {
        ["waitedMS"]=>
        int(0)
        ["results"]=>
        array(3) {
          [0]=>
          object(stdClass)#14 (2) {
            ["dis"]=>
            float(66308.6190421)
            ["obj"]=>
            object(stdClass)#13 (5) {
              ["_id"]=>
              object(MongoDB\BSON\ObjectID)#11 (1) {
                ["oid"]=>
                string(24) "57506d62f57802807471dd28"
              }
              ["name"]=>
              string(21) "XYZ Bagels Restaurant"
              ["contact"]=>
              object(stdClass)#12 (3) {
                ["phone"]=>
                string(12) "435-555-0190"
                ["email"]=>
                string(31) "XYZBagelsRestaurant@example.net"
                ["location"]=>
                array(2) {
                  [0]=>
                  float(-74.0707363)
                  [1]=>
                  float(40.5932157)
                }
              }
              ["stars"]=>
              int(4)
              ["categories"]=>
              array(3) {
                [0]=>
                string(6) "Bagels"
                [1]=>
                string(10) "Sandwiches"
                [2]=>
                string(6) "Coffee"
              }
            }
          }
          [1]=>
          object(stdClass)#18 (2) {
            ["dis"]=>
            float(69014.6014737)
            ["obj"]=>
            object(stdClass)#17 (5) {
              ["_id"]=>
              object(MongoDB\BSON\ObjectID)#15 (1) {
                ["oid"]=>
                string(24) "57506d62f57802807471dd39"
              }
              ["name"]=>
              string(20) "Green Feast Pizzeria"
              ["contact"]=>
              object(stdClass)#16 (3) {
                ["phone"]=>
                string(12) "840-555-0102"
                ["email"]=>
                string(30) "GreenFeastPizzeria@example.com"
                ["location"]=>
                array(2) {
                  [0]=>
                  float(-74.1220973)
                  [1]=>
                  float(40.6129407)
                }
              }
              ["stars"]=>
              int(2)
              ["categories"]=>
              array(2) {
                [0]=>
                string(5) "Pizza"
                [1]=>
                string(7) "Italian"
              }
            }
          }
          [2]=>
          object(stdClass)#22 (2) {
            ["dis"]=>
            float(69975.5031089)
            ["obj"]=>
            object(stdClass)#21 (5) {
              ["_id"]=>
              object(MongoDB\BSON\ObjectID)#19 (1) {
                ["oid"]=>
                string(24) "57506d62f57802807471dd35"
              }
              ["name"]=>
              string(14) "XYZ Coffee Bar"
              ["contact"]=>
              object(stdClass)#20 (3) {
                ["phone"]=>
                string(12) "644-555-0193"
                ["email"]=>
                string(24) "XYZCoffeeBar@example.net"
                ["location"]=>
                array(2) {
                  [0]=>
                  float(-74.0166091)
                  [1]=>
                  float(40.6284767)
                }
              }
              ["stars"]=>
              int(5)
              ["categories"]=>
              array(4) {
                [0]=>
                string(6) "Coffee"
                [1]=>
                string(4) "Cafe"
                [2]=>
                string(6) "Bakery"
                [3]=>
                string(10) "Chocolates"
              }
            }
          }
        }
        ["stats"]=>
        object(stdClass)#23 (5) {
          ["nscanned"]=>
          int(11)
          ["objectsLoaded"]=>
          int(10)
          ["avgDistance"]=>
          float(68432.9078749)
          ["maxDistance"]=>
          float(69975.5031089)
          ["time"]=>
          int(0)
        }
        ["ok"]=>
        float(1)
      }
    }
    ["server_id"]=>
    int(1)
  }

Commands with Custom Read Preference  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Some commands, such as :manual:`createUser
</reference/command/createUser/>`, may only be executed on a
:term:`primary` replica set member or a :term:`standalone`.

The command helper methods in the
|php-library|, such as :phpmethod:`MongoDB\\Database::drop`,
know to apply their own :term:`read preference` if necessary. However,
the :phpmethod:`MongoDB\\Database::command` method is a generic method and 
defaults to the read preference of the
Database object on which it is invoked. To execute commands that require
specific read preference, specify the read preference in the ``$options``
parameter of the method.

The following example adds a user to the ``demo`` database 
and specifies a custom read preference:

.. code-block:: php

   <?php

   $db = (new MongoDB\Client)->demo;

   $cursor = $db->command(
       [
           'createUser' => 'username',
           'pwd' => 'password',
           'roles' => ['readWrite'],
       ],
       [
           'readPreference' => new MongoDB\Driver\ReadPreference(MongoDB\Driver\ReadPreference::RP_PRIMARY),
       ]
   );

   var_dump($cursor->toArray()[0]);

The output would then resemble::

   object(MongoDB\Model\BSONDocument)#8 (1) {
     ["storage":"ArrayObject":private]=>
     array(1) {
       ["ok"]=>
       float(1)
     }
   }

View Command Results
--------------------

View Single Result Documents
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The :phpmethod:`MongoDB\\Database::command()` method returns a
:php:`MongoDB\\Driver\\Cursor <mongodb-driver-cursor>` object. 

Many MongoDB commands return their responses as a single document in an
array. To read the command response, you may either iterate on the
cursor and access the first document, or access the first result in the
array, as in the following:

.. code-block:: php

   <?php

   $database = (new MongoDB\Client)->demo;

   $cursor = $database->command(['ping' => 1]);

   var_dump($cursor->toArray()[0]);

The output would then resemble::

   object(MongoDB\Model\BSONDocument)#2 (1) {
     ["storage":"ArrayObject":private]=>
     array(1) {
       ["ok"]=>
       float(1)
     }
   }

Iterate Results from a Cursor
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Some commands, such as :manual:`listCollections
</reference/command/listCollections/>`,
return their results via an iterable cursor. To view the results,
iterate through the cursor. 

The following example lists the collections in the ``demo`` database by
iterating through the cursor returned by the ``listCollections`` command
using a ``foreach`` loop:

.. code-block:: php

   <?php

   $database = (new MongoDB\Client)->demo;

   $cursor = $database->command(['listCollections' => 1]);

   foreach ($cursor as $collection) {
       echo $collection['name'], "\n";
   }

The output would then be a list of the values for the ``name`` key,
for instance::

   persons
   posts
   zips

.. note::

   At the *protocol* level, commands that support a cursor
   return a single result document with the essential ingredients for
   constructing the command cursor (i.e. the cursor's ID, namespace, and
   the first batch of results). In the PHP driver implementation, the
   :php:`executeCommand() <mongodb-driver-manager.executecommand>`
   method detects the single result and constructs the iterable command
   cursor, which is returned rather than the base result document.