Pdf footer customize

I made a white application to generate a pdf through the tcpdf library. I have to customize the footer. I tried to use the example https://tcpdf.org/examples/example_003 but I get the error Fatal error: Uncaught Error: Class ‘MYPDF’ not found in C … The library is created and activated.
Thanks for your help

I found the answer here, I hope it helps you.