如何使用PHP在MongoDB中实现数据的外部存储

<?php
   $mongoClient = new MongoClient(); // 连接MongoDB服务器
   $db = $mongoClient->selectDB("mydb"); // 选择数据库
   $collection = $db->selectCollection("mycollection"); // 选择集合
?>

<?php
   $document = array(
      "name" => "John",
      "age" => 25,
      "email" => "john@example.com"
   );
   $collection->insert($document);
?>

<?php
   $query = array("name" => "John");
   $cursor = $collection->find($query);
   foreach($cursor as $document){
      echo $document["name"]."<br/>";
      echo $document["age"]."<br/>";
      echo $document["email"]."<br/>";
   }
?>

<?php
   $query = array("name" => "John");
   $update = array('$set' => array("age" => 26));
   $options = array("upsert" => true);
   $collection->update($query, $update, $options);
?>

<?php
   $query = array("name" => "John");
   $collection->remove($query);
?>

<?php
   $command = 'mongoimport --db mydb --collection mycollection --file /path/to/data.json';
   exec($command);
?>

<?php
   $command = 'mongoexport --db mydb --collection mycollection --out /path/to/data.json';
   exec($command);
?>