/*
* Used to invalidate cache by three URIs and a timestamp
*
* Cache invalidation only happens after a certain predefined time has passed
* Two times are set, one for normal slow data, another for faster data (live)
* These are defined as constants CACHE_VALID and CACHE_VALID_LIVE
* The timestamp of the files on disk is used to check when last the files were written
* and then invalidated if that time is longer than set time
*
* @one (string) first URI, default "default"
* @two (string) second URI, default "index"
* @three (string) third URI, default "index"
* @valid (int) valid time in minutes
* @return (null)
*/


function invalidate_cache($one = 'default', $two = 'index', $three = 'index', $valid = CACHE_VALID) {
    //Check if dir exists
    $path = BASE_SERVER_PATH.'application/cache/'.$one.'+'.$two.'+'.$three.'/';
    if(is_dir($path)) {
        //If request is live data, use shorter update
        if (in_array('live', array($one, $two, $three)) || in_array('index', array($one, $two, $three)))
            $valid = CACHE_VALID_LIVE;
        //Check cache, invalidate after set time
        $cache_mod = filemtime($path.'.');
        $time = (int) ((time() - $cache_mod) / 60);
        if ($time > $valid) {
            //Remove cache. First delete files then rm folder
            array_map('unlink', glob($path.'*'));
            rmdir($path.'/');
        }//end if cache still valid
    }//end if dir exists
}//end invalidate_cache