Checks if this is the default read concern

# MongoDB\Driver\ReadConcern::isDefault

(mongodb >=1.3.0)

MongoDB\Driver\ReadConcern::isDefault — Checks if this is the default read concern

### Description

final public MongoDB\Driver\ReadConcern::isDefault(): bool

Returns whether this is the default read concern (i.e. no options are specified). This method is primarily intended to be used in conjunction with MongoDB\Driver\Manager::getReadConcern() to determine whether the Manager has been constructed without any read concern options.

The driver will not include a default read concern in its read operations (e.g. MongoDB\Driver\Manager::executeQuery()) in order order to allow the server to apply its own default. Libraries that access the Manager's read concern to include it in their own read commands should use this method to ensure that default read concerns are left unset.

### Parameters

This function has no parameters.

### Return Values

Returns `true` if this is the default read concern and `false` otherwise.

### Errors/Exceptions

- Throws MongoDB\Driver\Exception\InvalidArgumentException on argument parsing errors.

### Examples

Example #1 MongoDB\Driver\ReadConcern::isDefault() example

`<?php
$rc = new MongoDB\Driver\ReadConcern(null);
var_dump($rc->isDefault());
$rc = new MongoDB\Driver\ReadConcern(MongoDB\Driver\ReadConcern::MAJORITY);
var_dump($rc->isDefault());
$manager = new MongoDB\Driver\Manager('mongodb://127.0.0.1/?readConcernLevel=majority');
$rc = $manager->getReadConcern();
var_dump($rc->isDefault());
$manager = new MongoDB\Driver\Manager('mongodb://127.0.0.1/');
$rc = $manager->getReadConcern();
var_dump($rc->isDefault());
?>`

The above example will output:

    bool(true)
    bool(false)
    bool(false)
    bool(true)

### See Also

- MongoDB\Driver\Manager::getReadConcern() - Return the ReadConcern for the Manager
- » Read Concern reference

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