laravel 5.6使用另一个服务器数据库

Am new in laravel I want to connect two database in my laravel project.

• 1st database in same server.
• 2nd database in another server.

This question already asked but that not relate my question.

I tried this code:

.env

1st database connection

DB_CONNECTION=mysql
DB_HOST=127.0.0.1
DB_PORT=3306
DB_DATABASE=thedaldb
DB_USERNAME=root
DB_PASSWORD=

2nd database connection

DB_CONNECTION_SECOND=mysql
DB_HOST_SECOND=127.0.0.1
DB_PORT_SECOND=3306
DB_DATABASE_SECOND=delivery_test
DB_USERNAME_SECOND=thedal
DB_PASSWORD_SECOND=thedal

app/config/database.php

2nd database connection

'onlineorder' => [
            'driver'    => env('DB_CONNECTION_SECOND'),
            'host'      => env('DB_HOST_SECOND'),
            'port'      => env('DB_PORT_SECOND'),
            'database'  => env('DB_DATABASE_SECOND'),
            'username'  => env('DB_USERNAME_SECOND'),
            'password'  => env('DB_PASSWORD_SECOND'),
        ],

I don't know what is added in 2nd database connection DB_HOST_SECOND ?