Deactivated error_reporting on the server according to the
manual. Situation's the same with no PDF generated.
disabling the Strict standards errors reporting on your server
Could you please elaborate? No messages were displayed before activating Error Reporting as suggested.
ps : I assure you that passing over the vm invoices' related Apache logs to you does not mean I'm asking the meaning of Apache status Codes. e.g. I should have reported the Apache log straight rather than "what does the 304 means ? (folloowed by the vminvoice&controller related Apache log)". May have misguided you on my motivation.