labels.php seems to be set up for Avery L7163 (14 labels per A4 sheet). For other layouts you need to enter all the measurements.
sample.php works if "format" is changed from PDF to WORD (outputs .doc, not docx). If you need PDF then save as PDF from the Word doc worked OK.
Label contents (address details) are hard-coded into sample.php
I'd written something more versatile using the FPDF library (uses PHP to create PDFs) a few years ago but it relied on an obsolete version of PHP. I see FPDF has been updated now so I need to find my old code but that too may have needed PHP3.