I tried to get max-age=0 to Cache-Control -header, and my first attempt was:
$controls = array ('no-cache', 'must-revalidate', 'no-store', 'max-age' => 0);
Resulting headers were:
Cache-Control: no-cache, must-revalidate, no-store, 0
Proper result can be achieved by using 'max-age=0' as value, but I think that it might be good to support key-value pairs also.