Fatal error: Uncaught Error: Class 'PDFMerger\TCPDI' not found in

[epanagio]

I have

include 'PDFMerger.php';
use PDFMerger\PDFMerger;
require_once 'PDFMerger.php';

$pdf = new PDFMerger;

$pdf->addPDF('t1.pdf', '1, 3, 4')
->addPDF('t2.pdf', '1-2')
->merge('file', 'out.pdf');

and I receive the following error/warning

Warning: "continue" targeting switch is equivalent to "break". Did you mean to use "continue 2"? in /Users/epanagio/Sites/play2/PDFMerger-master/tcpdf/tcpdf.php on line 17778

Fatal error: Uncaught Error: Class 'PDFMerger\TCPDI' not found in /Users/epanagio/Sites/play2/PDFMerger-master/PDFMerger.php:87 Stack trace: #0 /Users/epanagio/Sites/play2/PDFMerger-master/sample.php(10): PDFMerger\PDFMerger->merge('file', 'out.pdf') #1 {main} thrown in /Users/epanagio/Sites/play2/PDFMerger-master/PDFMerger.php on line 87

Based on another user's entry I modified and added

$fpdi = new TCPDI;

and now I receive:

Fatal error: Uncaught Error: Class 'TCPDI' not found in /Users/epanagio/Sites/play2/PDFMerger-master/sample.php:3 Stack trace: #0 {main} thrown in /Users/epanagio/Sites/play2/PDFMerger-master/sample.php on line 3

The files are stored in:

-rwxrwxrwx@ 1 epanagio staff 5248 Nov 16 2017 PDFMerger.php
-rwxrwxrwx@ 1 epanagio staff 1168 Nov 16 2017 README.md
-rwxrwxrwx@ 1 epanagio staff 558 Nov 16 2017 composer.json
-rwxrwxrwx@ 1 epanagio staff 221 Mar 9 11:49 sample.php
-rwxrwxrwx@ 1 epanagio staff 2213007 Mar 3 21:33 t1.pdf
-rwxrwxrwx@ 1 epanagio staff 2225123 Mar 4 08:23 t2.pdf
drwxrwxrwx@ 19 epanagio staff 608 Nov 16 2017 tcpdf

I changed the permissions to be 777 as a test.

How do I get rid of that fatal error?