<?php
$m = new MongoClient();
$c = $m->test->users;
$c->setReadPreference(MongoClient::RP_SECONDARY, array(
array('dc' => 'east', 'use' => 'reporting'),
array('dc' => 'west'),
array(),
));
var_dump($c->getReadPreference());
?>
array(2) {
["type"]=>
string(9) "secondary"
["tagsets"]=>
array(3) {
[0]=>
array(2) {
["dc"]=>
string(4) "east"
["use"]=>
string(9) "reporting"
}
[1]=>
array(1) {
["dc"]=>
string(7) "west"
}
[2]=>
array(0) {
}
}
}