php - Mongodb 不使用 php 获取嵌入式文档

Question

这是不获取嵌入文档的代码。

<?php 
   include 'vendor/dbcon.php';
       $documentlist = $state -> find(['s_name' => 'West Bengal'],
            ['projection' =>  ['_id' => 0, 'places._id' => 1]] );

    foreach ($documentlist as $doc) {
     echo $doc["places._id"] . "\n";
   }
 ?>

ERROR shows: Notice: Undefined index: places._id in C:\xampp\htdocs\Education\Home.php on line 130

如果代码是这样的:

foreach ($documentlist as $doc) {
         echo $doc["_id"] . "\n";
       }

then ERROR:: Notice: Undefined index: _id in C:\xampp\htdocs\Education\Home.php on line 130

数据库结构:Mongodb

 db.state.find().pretty()

{
        "_id" : "state1",
        "s_name" : "West Bengal",
        "places" : [
                {
                        "_id" : "Bardhaman",
                        "pin" : "754216"
                },
                {
                        "_id" : "Jalpaiguri",
                        "pin" : "754217"
                }
        ]
}

请帮助我如何打印所有 places._id 列表(例如 Bardhaman、Jalpaiguri)

Answer 1

投影没有问题，只是要访问的符号是 PHP 符号，而不是在 PHP 中的“点符号”。当然“places”是一个数组，所以你需要迭代:

  $documentlist = $state->find([],[ '_id' => 0, 'places._id' => 1 ]);

  foreach ($documentlist as $doc) {
    foreach($doc['places'] as $place) {
      echo $place['_id'] . "\n";
    }
  }

产生:

Bardhaman
Jalpaiguri