MongoCursor::setReadPreference

(PECL mongo >=1.3.3)

Set the read preference for this query

public MongoCursor MongoCursor::setReadPreference ( string $read_preference [, array $tags ] )

Parameters:

read_preference

The read preference mode: MongoClient::RP_PRIMARY, MongoClient::RP_PRIMARY_PREFERRED, MongoClient::RP_SECONDARY, MongoClient::RP_SECONDARY_PREFERRED, or MongoClient::RP_NEAREST.

tags

An array of zero or more tag sets, where each tag set is itself an array of criteria used to match tags on replica set members.

Returns:

Returns this cursor.

Exception:

Emits E_WARNING if either parameter is invalid, or if one or more tag sets are provided with the MongoClient::RP_PRIMARY read preference mode.

Examples:

MongoCursor::setReadPreference() tag set array syntax example

<?php
 
$m = new MongoClient();
$cursor = $m->test->users->find();
 
// Prefer the nearest server in the "east" data center also used for reporting,
// but fall back to a server in the "west" data center
$cursor->setReadPreference(MongoClient::RP_NEAREST, array(
    array('dc' => 'east', 'use' => 'reporting'),
    array('dc' => 'west'),
));
?>