HTTP_HEADER is not pass to POST
Just try to implement GLPI, work like charm except for every action button outside login, i receive this message from GLPI:
L'action que vous avez demandée n'est pas autorisée. Recharger la page précédente avant de faire une action à nouveau.
I think is related to POST action.
I have skipped the LLNG call and manually pass teh header with the same result. As GLPI is documented on your docs there probably something missing for NGINX