Without a database, without a SaaS platform, without an ERP

When the French e-invoicing reform (RFE) started becoming a real deadline, I needed to make my billing system compliant.

Not by switching to a SaaS platform.

Not by plugging into an ERP. But by integrating the Factur-X standard directly into an existing PHP stack, deployed on a standard Apache server.

This article is about how I did it, what the standard actually requires, and what the real technical challenges were.

What is Factur-X, really?

Factur-X is a franco-german standard for structured electronic invoicing. It is built on two layers:

A PDF/A-3 file — not just a regular PDF, but a long-term archiving format defined by ISO 19005-3

An embedded XML file compliant with the EN16931 European standard, profile Comfort

The PDF is human-readable. The XML is machine-readable. Both are mandatory.…