laravel include php(sdk) use psr-4 is class not found

Excuse me, I want to use this sdk GitHub

I try include file php into laravel controller , but is not work.

then, I'll update composer.json, using PSR-4 .. is class XXX/XXX/ not found..

how can I do? please help me, thanks~

composer.json

"autoload": {
    "classmap": [
        "database"
    ],
    "psr-4": {
        "App\\": "app/",
        "ECPaySDK\\": "ECPaySDK/"
    }
},

my controller

<?php

namespace App\Http\Controllers;
namespace ECPaySDK;
use Illuminate\Http\Request;
use Mail;
use App\Http\Requests;
use App\Travel_user;
use App\Travel_user_place;
use App\Place;
use App\Files;
use App\House;
use DB;
use Illuminate\Support\Facades\File;
class BackendController extends Controller

via Bruce