Detailed discussion of PHP caching technology_PHP tutorial-PHP Tutorial-php.cn

Detailed discussion of PHP caching technology_PHP tutorial

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Release： 2016-07-13 10:52:52

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1. Introduction

PHP, a web design script language that has emerged in recent years. Due to its power and scalability, it has made great progress in recent years. Compared with traditional ASP websites, PHP has an absolute advantage in speed. If you want to convert mssql For example, php takes 40 seconds to process 60,000 pieces of data, and asp takes no less than 2 minutes. However, as the website has more and more data, we are eager to call the data faster. We do not need to delete it from the database every time. We can retrieve it from other places. , such as a file, or a certain memory address, this is PHP’s caching technology, that is, Cache technology.

2. In-depth analysis

Generally speaking, the purpose of caching is to put data in one place to make access faster. There is no doubt that memory is the fastest, but can hundreds of M of data be stored in it? This is unrealistic, of course. Sometimes it is temporarily placed in the server cache. For example, if the ob_start() cache page is turned on, the page content will be cached in the memory before sending the file header. Until the page output is automatically cleared, or waiting for the return of ob_get_contents, or it is cleared by ob_end_clean display , this can be well utilized in the generation of static pages and can be well reflected in templates. This article of mine discusses it in depth: Talking about generating static pages with PHP. This is a way, but it is temporary. Sexual, is not a good way to solve our problems.

In addition, there is an object application in ASP, which can save public parameters. This is also a bit of caching, but in PHP, I have not seen developers produce such objects so far. Indeed, there is no need. ASP.NET page caching technology We use viewstate, and cache is file association (not necessarily accurate). When the file is modified, the cache is updated. If the file is not modified and does not time out (note 1), the cache is read and the result is returned. This is the idea. See Look at this source code:

class cache{
/*
Class Name: cache
Description: control to cache data,$cache_out_time is an array to save cache date time out.
Version: 1.0
Author: old farmer cjjer
Last modify:2006-2-26
Author URL: http://www.cjjer.com
*/
private $cache_dir;
private $expireTime=180;//The cache time is 60 seconds
function __construct($cache_dirname){
if(!@is_dir($cache_dirname)){
if(!@mkdir($cache_dirname,0777)){
$this->warn('The cache file does not exist and cannot be created, it needs to be created manually.');
return false;
}
}
$this->cache_dir = $cache_dirname;
}
function __destruct(){
echo 'Cache class bye.';
}

function get_url() {
if (!isset($_SERVER['REQUEST_URI'])) {
$url = $_SERVER['REQUEST_URI'];
}else{
$url = $_SERVER['script_NAME'];
$url .= (!empty($_SERVER['QUERY_STRING'])) ? '?' . $_SERVER['QUERY_STRING'] : '';
}

return $url;
}

function warn($errorstring){
echo "An error occurred:

".$errorstring."

";
}

function cache_page($pageurl,$pagedata){
if(!$fso=fopen($pageurl,'w')){
$this->warns('Unable to open cache file.');//trigger_error
return false;
}
if(!flock($fso,LOCK_EX)){//LOCK_NB, exclusive lock
$this->warns('Unable to lock cache file.');//trigger_error
return false;
}
if(!fwrite($fso,$pagedata)){//Write byte stream, serialize to write other formats
$this->warns('Unable to write to cache file.');//trigger_error
return false;
}
flock($fso,LOCK_UN);//Release lock
fclose($fso);
return true;
}

function display_cache($cacheFile){
if(!file_exists($cacheFile)){