session_cache_limiter() returns the name of the current cache limiter. If cache_limiter is specified, the name of the current cache limiter is changed to the new value.
The cache limiter controls the cache control HTTP headers sent to the client. These headers determine the rules by which the page content may be cached. Setting the cache limiter to nocache, for example, would disallow any client-side caching. A value of public, however, would permit caching. It can also be set to private, which is slightly more restrictive than public.
The cache limiter is reset to the default value stored in session.cache_limiter at request startup time. Thus, you need to call session_cache_limiter() for every request (and before session_start() is called).
Note: This function was added in PHP 4.0.3.