(PECL mongo >=1.3.0)
MongoDB::setReadPreference — Set the read preference for this database
$read_preference
[, array $tags
] ) : boolread_preferenceThe read preference mode: MongoClient::RP_PRIMARY, MongoClient::RP_PRIMARY_PREFERRED, MongoClient::RP_SECONDARY, MongoClient::RP_SECONDARY_PREFERRED, or MongoClient::RP_NEAREST.
tagsAn 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 TRUE on success, or FALSE otherwise.
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.
Example #1 MongoDB::setReadPreference() tag set array syntax example
<?php
$m = new MongoClient();
$db = $m->test;
// Prefer the nearest server in the "east" data center also used for reporting,
// but fall back to a server in the "west" data center
$db->setReadPreference(MongoClient::RP_NEAREST, array(
array('dc' => 'east', 'use' => 'reporting'),
array('dc' => 'west'),
));
?>