PHP cache class

 define('CACHE_ROOT', dirname(__FILE__).'/cache'); //Cache storage directory
 define('CACHE_TIME', 1800); //Cache time unit seconds
 define( 'CACHE_FIX','.html');
 $CacheName=md5($_SERVER['REQUEST_URI']).CACHE_FIX; //Cache file name
 $CacheDir=CACHE_ROOT.'/'.substr($CacheName,0,1 );//Cache file storage directory
 $CacheUrl=$CacheDir.'/'.$CacheName;//The complete path of the cache file
 //The cache is only cached after GET request. After POST, you generally want to see the latest results
 if ($_SERVER['REQUEST_METHOD']=='GET'){
 //If the cache file exists and has not expired, read it out.
 if(file_exists($CacheName) && time()-filemtime($CacheName) $fp=fopen($CacheName,'rb');
 fpassthru($fp);
 fclose($fp) ;
 exit;
 }
 //Check whether the folder exists, create it if it does not exist
 elseif(!file_exists($CacheDir)){
 if(!file_exists(CACHE_ROOT)){
 mkdir(CACHE_ROOT,0777);
 chmod (CACHE_ROOT,0777);
 }
 mkdir($CacheDir,0777);
 chmod($CacheDir,0777);
 }
 //Callback function, this function is automatically called when the program ends
 function AutoCache($contents){
 global $CacheUrl;
 $fp=fopen($CacheUrl,'wb');
 fwrite($fp,$contents);
 fclose($fp);
 chmod($CacheUrl,0777);
 //Generate new While caching, all old caches are automatically deleted to save space and can be ignored.
 //DelOldCache();
 return $contents;
 }
 function DelOldCache(){
 chdir(CACHE_ROOT);
 foreach (glob("*/*".CACHE_FIX) as $file){
 if(time() -filemtime($file)>CACHE_TIME)unlink($file);
 }
 }
 //Callback function auto_cache
 ob_start('AutoCache');
 }else{
 //Delete the cache file if it is not a GET request.
 if(file_exists($CacheUrl))unlink($CacheUrl);
 }
?>