如何在 php-mongodb 中编写带有条件的查找查询

我在php-monogodb中查找查询时遇到问题。 没有条件find()工作正常，但是在方法中使用条件find()它不会给出任何结果。如何解决这个问题？

$connection = new Mongo();
$db = $connection->selectDB('db1');
$collection = $db->selectCollection('customers');
$cursor = $collection->find(array('CUSTOMER_ID' => $id));
$num_docs = $cursor->count();
if($num_docs > 0)
{
    foreach($cursor as $obj)
    {
        echo 'Customer-Id: '.$obj['CUSTOMER_ID']."'n";
        echo 'Customer Name: '.$obj['CUST_FIRST_NAME']." ".$obj['CUST_LAST_NAME']."'n";
        echo 'Customer Email: '.$obj['CUST_EMAIL']."'n";
        echo "'n'n'n";
    }
}

在 var_dump（$cursor->explain（）） 之后;它打印：

array (size=3)
  'queryPlanner' => 
    array (size=6)
      'plannerVersion' => int 1
      'namespace' => string 'db1.customers' (length=13)
      'indexFilterSet' => boolean false
      'parsedQuery' => 
        array (size=1)
          'CUSTOMER_ID' => 
            array (size=1)
              ...
      'winningPlan' => 
        array (size=3)
          'stage' => string 'COLLSCAN' (length=8)
          'filter' => 
            array (size=1)
              ...
          'direction' => string 'forward' (length=7)
      'rejectedPlans' => 
        array (size=0)
          empty
  'executionStats' => 
    array (size=7)
      'executionSuccess' => boolean true
      'nReturned' => int 0
      'executionTimeMillis' => int 1
      'totalKeysExamined' => int 0
      'totalDocsExamined' => int 325
      'executionStages' => 
        array (size=14)
          'stage' => string 'COLLSCAN' (length=8)
          'filter' => 
            array (size=1)
              ...
          'nReturned' => int 0
          'executionTimeMillisEstimate' => int 0
          'works' => int 327
          'advanced' => int 0
          'needTime' => int 326
          'needYield' => int 0
          'saveState' => int 2
          'restoreState' => int 2
          'isEOF' => int 1
          'invalidates' => int 0
          'direction' => string 'forward' (length=7)
          'docsExamined' => int 325
      'allPlansExecution' => 
        array (size=0)
          empty
  'serverInfo' => 
    array (size=4)
      'host' => string 'deadpool' (length=8)
      'port' => int 27017
      'version' => string '3.2.4' (length=5)
      'gitVersion' => string 'e2ee9ffcf9f5a94fad76802e28cc978718bb7a30' (length=40)

你能解释一下出了什么问题吗？