The principle of sending a PHP cache class

<?php

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; Cached filename $CacheDir =cache_root. ' /'. substr ($CacheName, 0, 1);//cache file storage Directory $CacheUrl = $CacheDir. ' /'. $CacheName//The full path of the cached file//get the request is cached, after post generally want to see the latest results   if ($_server[' request_method ']== ' get ') {   //if the cached file exists and does not expire, read it.   if (file_exists ($CacheName) && time ()-filemtime ($CacheName) <cache_time) {       $FP =fopen ($CacheName, ' RB ');      fpassthru ($fp);      fclose ($FP);       exit;   &nbsp}   //to determine whether a folder exists or not, create   elseif (!file_exists ( $CacheDir)) {      if (!file_exists (cache_root)) {        mkdir (cache_ root,0777);        chmod (cache_root,0777);      }      mkdir ($CacheDir, 0777;      chmod ($CacheDir, 0777);    }   //callback function, which automatically calls this function when the program ends     function Autocache ($contents) {      global $CacheUrl;       $fp = fopen ($CACHEURL, ' WB ');      fwrite ($fp, $contents);      fclose ($fp);      chmod ($CACHEURL, 0777);      //generates a new cache while automatically deleting all the old caches to save space and can be ignored.       //deloldcache ();     return $contents; &NBSP;&NBSP}   function Deloldcache () {      chdir (cache_root);      foreach (Glob ("*/*"). Cache_fix) as $file) {        if (Time ()-filemtime ($file) >cache_time) unlink ($file);     &NBSP}  &nbsp}   //callback function auto_cache    ob_start (' Autocache '); }else{    //Deletes the cached file if it is not a GET request.     if (file_exists ($CACHEURL)) unlink ($CACHEURL); }?>