some classes of an external php file not found in the laravel project

I am using an third party plugin to enable payment function in my laravel project. But third party only support php. Even they have provided some sample project to show how it worked in php but I have to put those files which includes functions in somewhere in my laravel project and also give them a namespace in the beginning of the file. After I define namespace for phpqrcode.php file, QRcode class still couldn't been found.

Here is the the url where system will need to access QRcode class.

I have put external php in libraries folder:

Here is the file which contains QRcode class and other classes.

via Chebli Mohamed