Summary of 9 major caching technologies in PHP_PHP Tutorial

Summary of the 9 major caching technologies in PHP

1. Full page static caching

That is to say, all pages are generated as html static pages. The static pages are directly accessed when users visit, without going through the process of PHP server parsing. This method is more common in CMS systems, such as dedecms;

A common implementation method is to use output caching:

Ob_start()
******Code to run************
$content = Ob_get_contents();
****Write cached content to html file*****
Ob_end_clean();

2. Partial cache of the page

This method is to statically cache the infrequently changing parts of a page, while frequently changing blocks are not cached, and are finally assembled together for display; this can be achieved using a method similar to ob_get_contents, or using something similar to ESI. The page fragment caching strategy of this class is used to cache relatively static fragment parts in dynamic pages (ESI technology, please Baidu, not detailed here).

This method can be used for example, on product pages in malls;

3. Data cache

As the name suggests, it is a way of caching data; for example, when a certain product information in the mall is requested using the product ID, data including store information, product information, etc. can be obtained. At this time, these can be The data is cached in a PHP file, and the file name contains the product ID to create a unique identifier; the next time someone wants to view this product, they will first directly adjust the information in this file without querying the database; in fact, the cache file is cached is just a php array;

This method is used in the Ecmall mall system;

4. Query cache

In fact, this is the same idea as data caching, which is to cache according to the query statement; cache the data obtained by the query in a file. The next time the same query is encountered, the data will be directly transferred from this file first. I will check the database again; but the cache file name here may need to be uniquely identified based on the query statement;

Caching based on time changes

Actually, this is not a real caching method; the caching technologies 2, 3, and 4 above generally use time change judgment; that is, you need to set a valid time for cached files. Within this valid time, the same The content of the cache file will be fetched first when accessing, but if the set cache time is exceeded, the data needs to be re-obtained from the database and the latest cache file will be generated; for example, I set the homepage of our mall to be updated every 2 hours;

5. Cache according to content changes

This is not an independent caching technology and needs to be used in combination; that is, when the database content is modified, the cache file will be updated immediately;

For example, in a mall with a lot of traffic and a lot of products, the product list must be relatively large, and the pressure on this table is also relatively heavy; we can page cache the product display page;

When the merchant modifies the product information in the background, click Save, and we will update the cache file at the same time; then, when the buyer accesses the product information, he actually accesses a static page and does not need to access the database. ;

Just imagine, if the product page is not cached, then every time you access a product, you have to check the database. If 100,000 people browse the product online, the server will be under great pressure;

6. Memory cache

When it comes to this, the first thing you may think of is Memcached; memcached is a high-performance distributed memory cache server. The general purpose of use is to reduce the number of database accesses by caching database query results to increase the speed and scalability of dynamic web applications.

It caches the information that needs to be cached into the system memory. When the information needs to be obtained, it is fetched directly from the memory; the more commonly used method is the key–>value method;

$memcachehost = '192.168.6.191';
$memcacheport = 11211;
$memcachelife = 60;
$memcache = new Memcache;
$memcache->connect($memcachehost,$memcacheport) or die ("Could not connect");
$memcache->set('key','cache content');
$get = $memcache->get($key); //Get information
?>

7. apache cache module

After apache is installed, it is not allowed to be cached. If an external cache or squid server requires web acceleration, it needs to be set in httpd.conf. Of course, the premise is that the mod_cache module must be activated when installing apache.

When installing apache: ./configure –enable-cache –enable-disk-cache –enable-mem-cache

8. php APC cache extension

Php has an APC cache extension, which is php_apc.dll under Windows. You need to load this module first, and then configure it in php.ini:

[apc]
extension=php_apc.dll
apc.rfc1867 = on
upload_max_filesize = 100M
Post_max_size = 100M
apc.max_file_size = 200M
upload_max_filesize = 1000M
Post_max_size = 1000M
​​ max_execution_time = 600; ​ Maximum time value (seconds) for each PHP page to run, default 30 seconds
max_input_time = 600; Maximum time required for each PHP page to receive data, default 60
Memory_limit = 128M; Maximum memory consumed by each PHP page, default 8M

9. Opcode cache

We know that the execution process of PHP can be shown in the following figure:

First the PHP code is parsed into Tokens, then compiled into Opcode code, and finally the Opcode code is executed and the result is returned; therefore, for the same PHP file, its Opcode code can be cached the first time it is run, and the Opcode code can be executed next time When viewing the page, it will directly find the opcode code in the cache and execute the last step directly, without the need for intermediate steps.

The more well-known ones are XCache, Turck MM Cache, PHP Accelerator, etc.