在 PHP 中检索 Mongo 集合的字段

Question

我尝试在光标上使用fields() 方法：

<?php
$mongo  = new Mongo("mongodb://localhost");
print_r($mongo);

$db = $mongo->test;

// access collection
$collection = $db->test;

// execute query
// retrieve all documents
print_r($test);

$cursor = $collection->find();
print_r($cursor);

$fields = $cursor->fields(array("summary" => true));
print_r($fields);

输出是：

Mongo Object ( [connected] => 1 [status] => [server:protected] => [persistent:protected] => )
MongoCursor Object ( )
MongoCursor Object ( ) 

看起来驱动程序和连接工作正常，但我无法检索字段的独特摘要。

Answer 1

假设我们可以访问名为 db 的 mongodb 数据库，将从 MyCollection 检索数据并使用 MongoDB\Driver\Manager：

  $manager = new MongoDB\Driver\Manager( $DB_CONNECTION_STRING );

然后我们在这种情况下通过 name 检索数据，限制 2 个文档，并希望获得 only fields name em>、age 和 address 等等。 Projection 选项可用于指定应返回哪些字段，使用 0 排除并使用 1 包含：

  $filter = ['name' => 'John'];
  $options = [ 'projection' => ['_id' => 0, 'name' => 1, 'age' => 1, 'address' => 1], 'limit' => 2 ];
  $query = new MongoDB\Driver\Query($filter, $options);
  $manager->executeQuery('db.MyCollection', $query);

如果我们需要获取所有列，那么我们只需省略 projection 选项，如下所示：

  $filter = ['name' => 'daniel'];
  $options = [];
  $query = new MongoDB\Driver\Query($filter, $options);
  $manager->executeQuery('db.MyCollection', $query);

Answer 2

 const HOST = 'localhost';
 const PORT = 27017;
 const DBNAME = 'test';
 const COLLECTION = 'test';
 $connectionString = sprintf('mongodb://%s:%d', HOST, PORT);

 try {

        $connection = new Mongo($connectionString);
        $database = $connection->selectDB(DBNAME);

 } catch (MongoConnectionException $e) {

        throw $e;

}
$collection = $database->selectCollection(COLLECTION);

try{
        $query = array();
        $specifyKey = array("summary" => true);
        $cursor = $collection->find($query , $specifyKey);

}catch(MongoException $e) {

        die('Failed to find One data '.$e->getMessage());

}catch (MongoCursorException $e) {

    echo "error message: ".$e->getMessage()."\n";
    echo "error code: ".$e->getCode()."\n";
}

while ($cursor->hasNext()){

    $nextCursor = $cursor->getNext(); 
    //process next cursor
}

Answer 3

在 $cursor 变量之后尝试使用 foreach。它遍历游标结果。

foreach($cursor as $document) {  
 var_dump($document);  
}