Define the contents of the Cache-Control header.
If set to set to "public", proxies are adviced to cache the response, if set to "private", proxies are adviced to do not.
The maxage paramter controls the amount of seconds an entity is suggested to be cached. Many user agents won't even send a request for subsequent requests to the same resource within the specified time frame.
string [$cache = "public"] - whether to allow proxy caching
int [$maxage = 0] - maximum age of the cached entity