If you want to enable to disable PHP variable for all domains then you can do that using the below steps :
Here we have taken an example of safe_mode varibale
root@server
root@server
and just add the below lines in the safemode.conf file
<Location />
php_admin_flag safe_mode off
< /Location>
Finally restart the apache service on the server and it will work like a charm.
That's All !!