Laravel 5.4 with mongodb 3.2 - 无法解析mongodb URI

Question

/*  local.ERROR: MongoDB\Driver\Exception\InvalidArgumentException: Failed to 
    parse MongoDB URI: 'mongodb://:/'. Invalid host string in URI. in 
    D:\Xampp\htdocs\laravel_bdna\bdna\vendor\mongodb\mongodb\src\Client.php:84

我打印了mongodb URI IN LOG FILE

    [2017-11-28 02:35:16] local.INFO: 111111111111111111111111111111111111111  
    [2017-11-28 02:35:16] local.INFO: mongodb://maddyUser:Moji6251@localhost:27017/mad  
    [2017-11-28 02:35:16] local.INFO: 111111111111111111111111111111111111111  
    [2017-11-28 02:35:16] local.INFO: mongodb://maddyUser:Moji6251@localhost:27017/mad  
    [2017-11-28 02:35:16] local.INFO: 111111111111111111111111111111111111111  
    [2017-11-28 02:35:16] local.INFO: mongodb://maddyUser:Moji6251@localhost:27017/mad  
    [2017-11-28 02:35:16] local.INFO: 111111111111111111111111111111111111111  
    [2017-11-28 02:35:16] local.INFO: mongodb://maddyUser:Moji6251@localhost:27017/mad  
    [2017-11-28 02:35:16] local.INFO: 111111111111111111111111111111111111111  
    [2017-11-28 02:35:16] local.INFO: mongodb://:/  
    [2017-11-28 02:35:16] local.INFO: 111111111111111111111111111111111111111  
    [2017-11-28 02:35:16] local.ERROR: MongoDB\Driver\Exception\InvalidArgumentException: Failed to parse MongoDB URI: 'mongodb://:/'. Invalid host string in URI. in D:\Xampp\htdocs\laravel_bdna\bdna\vendor\mongodb\mongodb\src\Client.php:84

    #0 D:\Xampp\htdocs\laravel_bdna\bdna\vendor\mongodb\mongodb\src\Client.php(84): MongoDB\Driver\Manager->__construct('mongodb://:/', Array, Array)
    #1 D:\Xampp\htdocs\laravel_bdna\bdna\app\MongoBG\MongoBG.php(109): MongoDB\Client->__construct('mongodb://:/', Array, Array)
    #2 D:\Xampp\htdocs\laravel_bdna\bdna\app\Providers\MongoBGServiceProvider.php(68): App\MongoBG\MongoBG->__construct('mongodb://:/', Array, Array)*/