PHP

<?php
require_once __DIR__ . '/../config/database.php';
$capsule = new \Illuminate\Database\Capsule\Manager;

$db_names = array_keys($config['database']);

foreach($db_names as $name){
    $alis = $name;
    if($name === reset($db_names)) $alis = 'default';
    $capsule->addConnection($config['database'][$name], $alis);
}
$capsule->setAsGlobal();
$capsule->bootEloquent();

<?php
require_once __DIR__ . '/../vendor/autoload.php';

$router = new AltoRouter();

$router->map('GET|POST','/',
  'App\TopController::index',
  'home'
);

$match = $router->match();

if( is_array($match) && is_callable( $match['target'] ) ) {
  $params = explode("::", $match['target']);
  $action = new $params[0]();
  call_user_func_array(array($action, $params[1]) , $match['params']);
} else {
  header( $_SERVER["SERVER_PROTOCOL"] . ' 404 Not Found');
}

<?php
$config['database'] = [
    'main' => [
        'driver'    => 'sqlite',
        'database'  => __DIR__ . '/../database/main.sqlite',
    ],
];

// 個別DB設定を全部require
$req_dir = [__DIR__ . '/database/'];
foreach ($req_dir as $r) {
    foreach(glob($r.'*') as $file){
        if(is_file($file)){
            require_once $file;
        }
    }
}

<?php

use SomeModel;

class SomeController extends BaseController {
    public function someMethod()
    {
        $someModel = new SomeModel;
        $someModel->setConnection('DB2');
        $something = $someModel->find(1);
        return $something;
    }
}

public function register()
  {
     // 追記する-->
      $this->app->singleton('mailer', function ($app) {
          $app->configure('services');
          return $app->loadComponent('mail', 'Illuminate\Mail\MailServiceProvider', 'mailer');
      });
     // <--追記する
  }