__construct() публичный Метод

Files as stored across two collections, the first containing file meta information, the second containing chunks of the actual file. By default, fs.files and fs.chunks are the collection names used.
См. ссылку: http://php.net/manual/en/mongogridfs.construct.php
public __construct ( MongoDB $db, string $prefix = "fs", mixed $chunks = null )
$db MongoDB Database
$prefix string [optional]

Optional collection name prefix.
$chunks mixed [optional]
Документация по классу MongoGridFS
Пример #1
0
 /**
  * Constructor.
  *
  * @param \Mongator\Logger\LoggableMongoDB $db     A LoggableMongoDB instance.
  * @param string                           $prefix The prefix (optional, fs by default).
  */
 public function __construct(LoggableMongoDB $db, $prefix = 'fs')
 {
     $this->db = $db;
     $this->time = new Time();
     parent::__construct($db, $prefix);
 }