Laravel Argument 1 passed to App\Models\Recipients\AlertRecipient::__construct() must be an instance of App\Models\Recipients\string, string given,

Today, when the test plan task snipet, inventory below the warning value, time will automatically send a message to the mailbox

class SendInventoryAlerts extends Command
{
    /**
     * The name and signature of the console command.
     *
     * @var string
     */
    protected $signature = 'snipeit:inventory-alerts';

　You can see the name of the current command is

snipeit: inventory-alerts 

I use windows10 commissioning, start: 
1. Open cmd, cd .... into the project directory 
2. Enter snipeit: inventory-alerts, but this time there was an error message:

Finally found the reason is due to the php version, PHP version I'm using 5.6.27

3. Then, I went to modify environment variables and update the current version of php php7 
then re-open cmd, enter the above command, the effect appears as shown below, separated by about one second to do the old, flew to receive the message mail sent successfully