Sample XADES files

Hello!

I'm implementing XADES signature in PHP and I need to make sure I
understand well w3c spec of XADES.
I'm looking for sample (complete and valid) XADES files, and some
step-by-step example on how to generate every section inside XADES
file with valid values.
I noticed that some applications for electronic signature don't
strictly rely on w3c XADES spec, so I cannot trust their code.

Cheers,
Piotrek