(mongodb >=1.3.0)
MongoDB\Driver\WriteConcern::isDefault — Checks if this is the default write concern
Returns whether this is the default write concern (i.e. no options are specified). This method is primarily intended to be used in conjunction with MongoDB\Driver\Manager::getWriteConcern() to determine whether the Manager has been constructed without any write concern options.
The driver will not include a default write concern in its write operations (e.g. MongoDB\Driver\Manager::executeBulkWrite()) in order to allow the server to apply its own default, which may have been » modified. Libraries that access the Manager's write concern to include it in their own write commands should use this method to ensure that default write concerns are left unset.
此函数没有参数。
Returns true if this is the default write concern and false otherwise.
Example #1 MongoDB\Driver\WriteConcern::isDefault() example
<?php
$wc = new MongoDB\Driver\WriteConcern(1);
var_dump($wc->isDefault());
$manager = new MongoDB\Driver\Manager('mongodb://127.0.0.1/?w=majority');
$wc = $manager->getWriteConcern();
var_dump($wc->isDefault());
$manager = new MongoDB\Driver\Manager('mongodb://127.0.0.1/');
$wc = $manager->getWriteConcern();
var_dump($wc->isDefault());
?>
以上例程会输出：
bool(false) bool(false) bool(true)