“use setasignFpdiFpdi” command doesn’t work in php [duplicate]

I follow this tutorial https://transloadit.com/devtips/merging-pdf-documents-in-php-using-fpdi-and-fpdf/#install-fpdi-and-fpdf.

I installed packages by composer require setasign/fpdf:1.8.* and then composer require setasign/fpdi:^2.0.

Then I run in php -a:

require 'vendor/autoload.php';

use setasignFpdiFpdi;

$pdf = new Fpdi();

It throws error “PHP Warning: Uncaught Error: Class “Fpdi” not found in php shell code:1″.

But directly $pdf = new setasignFpdiFpdi(); without using use works. What is the reason?