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# MongoClient::__construct

(PECL mongoclient >=0.9.0)

MongoClient::__construct — Creates a new database connection object

### Description

public MongoClient::__construct() ([ string `$server` = "mongodb://localhost:27017" [, array `$options` = array("connect" => `TRUE`) ]] )

If no parameters are passed, this connects to "localhost:27017" (or whatever was specified in php.ini for mongo.default_host and mongo.default_port).

`server` should have the form:

    mongodb://[username:password@]host1[:port1][,host2[:port2:],...]/db

The connection string always starts with mongodb://, to indicate it is a connection string in this form.

If username and password are specified, the constructor will attempt to authenticate the connection with the database before returning. Username and password are optional and must be followed by an @, if specified.

At least one host must be given (port optional, always defaulting to 27017) and as many hosts as desired may be connected to. Host names are comma-separated and the constructor will return successfully if it connected to at least one host. If it could not connect to any of the hosts, it will throw a MongoConnectionException. Please see the Replica Sets section for information on how to connect to Replica Sets.

If you specified a username and password, you may specify a database to authenticate with. If db is not specified, "admin" will be used.

An optional query string may be used to specify extra options. The same options are supported through the `options` array as well, and are therefore redescribed there. See the examples below on how to set those options.

One part of the options governs how the driver reads from secondary nodes in a replica set environment. Extra information on how these read preferences work is available as well through the read preferences documentation page.

### Parameters

`server`

  The server name.

`options`

  An array of options for the connection. Currently available options include:

  - "connect"

    If the constructor should connect before returning. Default is `TRUE`. When set to `FALSE` the driver will automatically connect to the server whenever it is necessary to do a query. Alternatively, you can run MongoClient::connect() manually.

    Warning

    This option is not supported through the connection string.

  - "connectTimeoutMS"

    How long a connection can take to be opened before timing out in milliseconds.

  - "db"

    The database to authenticate against can be specified here, instead of including it in the host list. This overrides a database given in the host list.

  - "fsync"

    When fsync is set, all write operations on the database will block until the database server has flushed its database files to disk. This makes write operations a lot slower, but it guarantees that the write operation has succeeded and committed to disk. Please avoid using this option and use the journal option instead, perhaps in combination with the w option.

  - "journal"

    When journal is set, all write operations on the database will block until the database server has flushed the journal to disk. This makes the write operations marginally slower, but it guarantees that the write operation has succeeded and the operation can be recovered in case of total system failure.

  - "password"

    The password can be specified here, instead of including it in the host list. This is especially useful if a password has a "@" in it. This overrides a password set in the host list.

  - "readPreference"

    Specifies the read preference type. Read preferences provide you with control from which secondaries data can be read from.

    Allowed values are: `MongoClient::RP_PRIMARY`, `MongoClient::RP_PRIMARY_PREFERRED`, `MongoClient::RP_SECONDARY`, `MongoClient::RP_SECONDARY_PREFERRED` and `MongoClient::RP_NEAREST`.

    See the documentation on read preferences for more information.

  - "readPreferenceTags"

    Specifies the read preference tags as an array of strings. Tags can be used in combination with the readPreference option to further control which secondaries data might be read from.

    See the documentation on read preferences for more information.

  - "replicaSet"

    The name of the replica set to connect to. If this is given, the primary will be automatically be determined. This means that the driver may end up connecting to a server that was not even listed. See the replica set example below for details.

  - "socketTimeoutMS"

    How long a send or receive on a socket can take before timing out.

    > Note: This is a client side timeout. If an insert hits the "socketTimeoutMS" value there is no way to know if the server actually received the write or not.

  - "ssl"

    A boolean to specify whether you want to enable SSL for the connections to MongoDB. Extra options such as certificates can be set with SSL context options.

  - "username"

    The username can be specified here, instead of including it in the host list. This is especially useful if a username has a ":" in it. This overrides a username set in the host list.

  - "w"

    The w option specifies the Write Concern for the driver, which determines how long the driver blocks when writing. The default value is 1.

    This option is applicable when connecting to both single servers and replica sets. A positive value controls how many nodes must acknowledge the write instruction before the driver continues. A value of 1 would require the single server or primary (in a replica set) to acknowledge the write operation. A value of 3 would cause the driver to block until the write has been applied to the primary as well as two secondary servers (in a replica set).

    A string value is used to control which tag sets are taken into account for write concerns. "majority" is special and ensures that the write operation has been applied to the majority (more than 50%) of the participating nodes.

  - "wTimeoutMS"

    This option is used in combination with the "w" option. It controls how many milliseconds the server waits for the write concern to be satisfied. If it takes longer then the server signals to the driver that it took too long and the driver will throw a MongoCursorException exception.

  The following options are deprecated and should no longer be used:

  - "timeout"

    Deprecated alias for "connectTimeoutMS".

  - "wTimeout"

    Deprecated alias for "wTimeoutMS".

### Return Values

Returns a new database connection object.

### Errors/Exceptions

Throws MongoConnectionException if it tries and fails to connect to the database for all hostnames given. It will also throw a MongoConnnectionException if an invalid username or password is given. See MongoConnectionException documentation for common exceptions and their causes.

### Examples

Example #1 MongoClient::__construct() replica set example

This example shows how to connect the driver to a replica set. It assumes that there is a set of three servers: sf1.example.com, sf2.example.com, and ny1.example.com. The primary could be any one of these servers.

`<?php
// pass a comma-separated list of server names to the constructor
// Note that we don't need to pass in all the members of the replicaset, the driver
// will derive the full list.
$m1 = new MongoClient("mongodb://sf2.example.com,ny1.example.com", array("replicaSet" => "myReplSet"));
?>`

If the current primary fails, the driver will figure out which secondary server became the new primary and automatically start using that connection. Automatic failover will not work correctly if replicaSet is not specified.

At least one seed in the seed list must be up for the driver to connect to the replica set.

If you include seeds from two separate replica sets, behavior is undefined.

See the » core documentation on replica sets for more information.

Example #2 Connecting to a domain socket

In version 1.0.9+, you can use a UNIX domain socket to connect to an instance of MongoDB running locally. This should be slightly faster than using a network connection.

In version 1.5.0, the MongoDB server automatically opens a socket at /tmp/mongodb-<port>.sock. You can connect to this by specifying the path in your connection string:

`<?php
// MongoDB server running locally on port 20000
$m = new MongoClient("mongodb:///tmp/mongodb-20000.sock");
?>`

You can combine this with any other connections you'd like:

`<?php
// try to connect to the domain socket, fall back to localhost connection
$m = new MongoClient("mongodb:///tmp/mongodb-27017.sock,localhost:27017");
?>`

Example #3 MongoClient::__construct() authentication example

A user must exist in the admin database before attempting to use authentication. You can create one with the Mongo shell by running:

    > use admin
    switched to db admin
    > db.addUser("testUser", "testPass");
    {
            "_id" : ObjectId("4b21272fd9ab21611d19095c"),
            "user" : "testUser",
            "pwd" : "03b9b27e0abf1865e2f6fcbd9845dd59"
    }
    >

After creating a user with, in this case, username "testUser" and password "testPass", you can create an authenticated connection:

`<?php
$m = new MongoClient("mongodb://testUser:testPass@localhost");
?>`

Example #4 MongoClient::__construct() read preference example

`<?php
// Prefer the nearest server in the "east" data center
$uri = 'mongodb://rs1.example.com,rs2.example.com/';
$uri .= '?readPreference=nearest';
$uri .= '&readPreferenceTags=dc:east';
$m = new MongoClient($uri, array('replicaSet' => 'rs'));
?>`

See the read preferences section of this manual for further information.

Example #5 MongoClient::__construct() options example

Options can be passed both through the query string in the connection string, or as an array passed as second argument to the constructor.

Here we set the journal option to true and readPreference to secondary preferred as default for all write operations:

    <?php
    $m = new MongoClient("mongodb://localhost/?journal=true&readPreference=secondary");
    ?>

And now we do the same, but as an options array:

    <?php
    $options = array(
        'journal' => true,
        'readPreference' => 'secondary',
    );
    $m = new MongoClient("mongodb://localhost/", $options);
    ?>

Example #6 MongoClient::__construct() read preference example

`<?php
// Prefer the nearest server in the "east" data center
$uri = 'mongodb://rs1.example.com,rs2.example.com/';
$uri .= '?readPreference=nearest';
$uri .= '&readPreferenceTags=dc:east';
$m = new MongoClient($uri, array('replicaSet' => 'rs'));
?>`

See the read preferences section of this manual for further information.

### Changelog

Version | Description
--- | ---
1.4.0 | Added the "wTimeoutMS" option has replacement for "wTimeout".
1.3.4 | Added the "connectTimeoutMS" and "socketTimeoutMS" options.
1.3.0 | Added the "readPreference", "readPreferenceTags", "w" and "wTimeout" options.
1.2.0 | Added the "username" and "password" options. Removed the "persist" option, as all connections are now persistent. It can still be used, but it doesn't affect anything.

`"persist"`

  If the connection should be persistent. If set, the connection will be persistent. The string representation of the value is used as an ID for the connection, so two instances of MongoClient that are initialized with array("persist" => "foobar") will share the same database connection, whereas an instance initialized with array("persist" => "barbaz") will use a different database connection.

The "replicaSet" option now takes a string, not a boolean.

1.0.9 | Added the "replicaSet" option.
1.0.2 | Changed constructor to take an array of options. Pre-1.0.2, the constructor took the following parameters:

`server`

  The server name.

`connect`

  Optional boolean parameter specifying if the constructor should connect to the database before returning. Defaults to `TRUE`.

`persistent`

  If the connection should be persistent.

`paired`

  If the connection should be paired.

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