PHP CONFIG - ADMIN VALUE ENGINE

Hello. I got some Virtual Servers running and I need to apply a single change to the PHP config of each of them. The value I need to change is

php_admin_value engine ON/OFF

I need to have it commented or null, not ON nor OFF. In the GUI there are two fields, one to be filled with 'engine' and the other with 'on' or 'off'. How can I do it massively? I can't spend much time to edit each single config...please, help, I'm desperate!

Thank you all