Defining max-age to Cache-Control -headers more intuitively

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.