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## Authentication

If MongoDB is started with the --auth or --keyFile options, you must authenticate before you can do any operations with the driver. You may authenticate a connection by specifying the username and password in either the connection URI or the "username" and "password" options for MongoClient::__construct().

Example #1 Authenticating against the "admin" database

`<?php
// Specifying the username and password in the connection URI (preferred)
$m = new MongoClient("mongodb://${username}:${password}@localhost");
// Specifying the username and password via the options array (alternative)
$m = new MongoClient("mongodb://localhost", array("username" => $username, "password" => $password));
?>`

By default, the driver will authenticate against the admin database. You may authenticate against a different database by specifying it in either the connection URI or the "db" option for MongoClient::__construct().

Example #2 Authenticating against normal databases

`<?php
// Specifying the authentication database in the connection URI (preferred)
$m = new MongoClient("mongodb://${username}:${password}@localhost/myDatabase");
// Specifying the authentication database via the options array (alternative)
$m = new MongoClient("mongodb://${username}:${password}@localhost", array("db" => "myDatabase"));
?>`

If your connection is dropped, the driver will automatically attempt to reconnect and reauthenticate you.

Connecting
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PHP Manual