PHP tutorial: Summary of 9 major caching technologies in PHP

[Introduction] 1. Full-page static caching means that all pages are generated into html static pages. The static pages are directly accessed when users visit, without going through the PHP server parsing process. This method is more common in CMS systems, such as dedecms; a common implementation method is to use output caching: Ob

1, full page static cache

, that is, the page All HTML static pages are generated, which are static pages that users access directly when accessing, without going through the PHP server parsing process. This method is more common in CMS systems, such as dedecms; a common implementation method is to use output caching: Ob_start()******code to be run************$content = Ob_get_con

2. Partial caching of pages: In this method,

statically caches the parts of a page that do not change frequently, while blocks that change frequently are not cached, and are finally assembled together for display; you can It can be implemented using a method similar to ob_get_contents, or you can also use a page fragment caching strategy such as ESI to cache relatively static fragments in dynamic pages (ESI technology, please Baidu, not detailed here).
This method can be used for example, on product pages in the mall;
3. Data caching. As the name suggests,

is a way of caching data; for example, when a certain product information in the mall is When you use the product ID to request, you will get data including store information, product information, etc. At this time, you can cache these data into a php file. The file name contains the product ID to create a unique identifier; next time someone wants to view it When selecting this product, first directly adjust the information in this file without querying the database; in fact, what is cached in the cache file is a php array or the like; this method is used in the Ecmall mall system;
4. Query caching

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, it will be cached directly from this file. The data is adjusted inside, and the database will not be checked; but the cache file name here may need to be based on the query statement to establish a unique identifier;
Caching based on time changes In fact, this is not a real caching method; the above Caching technologies 2, 3, and 4 generally use time change judgment; that is, you need to set a valid time for the cached file. Within this valid time, the same access will first fetch the content of the cached file, but if it exceeds the set time Caching time requires re-obtaining data from the database and producing the latest cache file; 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 is updated immediately;
For example, in a shopping mall with a large flow of people and many products, the product table must be relatively large. This table The pressure is also relatively heavy; we can cache the product display page;
When the merchant modifies the product information in the background, click Save, we will update the cache file at the same time; then, when the buyer accesses the product information , actually accessing a static page without the need to access the database;
Just imagine, if the product page is not cached, then every time you access a product, you have to go to the database to check it. If there are 100,000 people browsing online products, the server will be under great pressure;
6. Memory cache

When it comes to this, the first thing that everyone 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','缓存的内容');
    $get = $memcache->get($key);       //获取信息?>

7. After the apache cache module 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 first module, 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 ;   每个PHP页面运行的最大时间值(秒)，默认30秒 
    max_input_time = 600 ;       每个PHP页面接收数据所需的最大时间，默认60 
    memory_limit = 128M ;       每个PHP页面所吃掉的最大内存，默认8M

9. Opcode cache We know that the execution process of php can be shown in the following figure:

First of all 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 next time the page is executed, it will be directly It will 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. tents();****Write the cached content into the html file*****Ob_end_clean();

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