Mongodb不用php获取嵌入文档

Question

这里是它没有嵌入文档的代码。

<?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的

db.state.find().pretty() 

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

请帮助我，我怎么能打印所有places._id列表（来自Bardhaman，Jalpaiguri）

Answer 1

投影没什么问题，它只是访问的符号是PHP符号，而不是PHP中的“Dot notation”。当然还有 “地方” 是一个数组，所以你需要遍历：

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

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

产地：

Bardhaman 
Jalpaiguri