MongoDb v4.2.1 聚合 - 如何在 php 7 代码中使用 join答案

【问题标题】：MongoDb v4.2.1 aggregation - How to use join in php 7 codeMongoDb v4.2.1 聚合 - 如何在 php 7 代码中使用 join
【发布时间】：2023-03-06 16:07:01
【问题描述】：

我正在使用 MongoDB 4.2 开发 PHP7。

我正在尝试使用聚合连接表。

我可以在 mongo 控制台上进行操作。

db.orders.aggregate([
    {
       $lookup: {
          from: "items",
          localField: "item",    // field in the orders collection
          foreignField: "item",  // field in the items collection
          as: "fromItems"
       }
    },
    {
       $replaceRoot: { newRoot: { $mergeObjects: [ { $arrayElemAt: [ "$fromItems", 0 ] }, "$$ROOT" ] } }
    },
    { $project: { fromItems: 0 } }
])

得到结果：

{ "_id" : 1, "item" : "almonds", "description" : "almond clusters", "instock" : 120, "price" : 12, "quantity" : 2 }
{ "_id" : 2, "item" : "pecans", "description" : "candied pecans", "instock" : 60, "price" : 20, "quantity" : 1 }

我想在 PHP 中做同样的事情，但没有得到结果：

我的 PHP 代码是：

<?php
public function demo_join() {

        global $mng; // $mng = new MongoDB\Driver\Manager("mongodb://localhost:27017");
        global $dbname;


        $command = new MongoDB\Driver\Command([
            'aggregate' => 'orders',
            'pipeline' => [
                ['$lookup' => ["from" => "items","localField" => "items","foreignField" => "items","as" => "fromItems"]],
            ],
        ]);
        //$cursor = $mng->executeCommand($dbname, $command);

        try {
            $cursor = $manager->executeCommand($dbname, $command);
        } catch(MongoDB\Driver\Exception $e) {
            echo $e->getMessage(), "\n";
            exit;
        }
    return $cursor;

}

?>

并收到此错误：

 Uncaught Error: Call to a member function executeCommand() on null in $cursor = $manager->executeCommand($dbname, $command);

还有一段时间

 Uncaught MongoDB\Driver\Exception\CommandException: The 'cursor' option is required, except for aggregate with the explain argument in

【问题讨论】：

标签： mongodb php-7.2

【解决方案1】：

好的，我得到了答案：

我添加了这一行：'cursor' => new stdClass

<?php
//mongo database join example
    public function test_join() {

        global $mng;
        global $dbname;


        $pipeline =  [['$lookup' => ["from" => "items","localField" => "items","foreignField" => "items","as" => "fromItems"]]];

        $aggregate = new \MongoDB\Driver\Command([
           'aggregate' => 'orders', 
           'cursor' => new stdClass,
           'pipeline' => $pipeline
        ]);

        $cursor = $mng->executeCommand($dbname, $aggregate);
        return $cursor;

    }

?>

现在，我可以得到结果了。

【讨论】：