Creating XML request and signing document with Gov agency in PHP

Hello,
need someone who will create XML request which should be sent to authorized agency for checking and signing sale on the prestashop webshop (sale authorization). Request must have data from completed order sent to the recipient server with digital certification (provided from us) and receiving approval with signature for that sale (approval is just a line of numbers).

I can provide docs and example done in magento.
This is for prestashop 1.7, so it’s PHP, MySQL, XML work.

Thanks!