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Detailed explanation of PHP caching mechanism_PHP tutorial
- WBOYOriginal
- 2016-07-15 13:28:41907browse
By using the universal caching technology of this site
Data caching: The data cache mentioned here refers to the database query PHP caching mechanism, each time When accessing a page, it will first check whether the corresponding cached data exists. If it does not exist, it will connect to the database, obtain the data, and serialize the query results and save them to a file. In the future, the same query results will be directly obtained from the cache table or file. obtained in.
The most widely used example is the search function of Discuz, which caches the result ID into a table and searches the cache table first when searching for the same keyword next time.
As a common method, when multiple tables are associated, generate an array and save the contents in the attached table to a field in the main table. When necessary, decompose the array. The advantage of this is that only one table can be read. , the disadvantage is that there will be many more steps to synchronize the two data. The database is always the bottleneck. Trading the hard disk for speed is the key point of this.
Page caching:
Every time you access a page, it will first check whether the corresponding cached page file exists. If it does not exist, connect to the database and get the data. Display the page and generate a cache page file at the same time, so that the page file will be effective the next time you visit. (Template engines and some common PHP caching mechanism classes on the Internet usually have this function)
Time-triggered caching:
Check whether the file exists and the timestamp is less than the set expiration Time, if the file modification timestamp is greater than the current timestamp minus the expiration timestamp, then use the cache, otherwise update the cache.
Content-triggered caching:
Force the PHP cache mechanism to be updated when data is inserted or updated.
Static cache:
The static cache mentioned here refers to static, directly generate text files such as HTML or XML, and regenerate them when there are updates, which is suitable For pages that don’t change much, I won’t talk about it.
The above content is a code-level solution. I directly CP other frameworks and am too lazy to change. The content is similar, it is easy to do, and can be used in several ways, but the following content is for the server End-end caching solution, non-code level, requires the cooperation of multiple parties to achieve
Memory cache:
Memcached is a high-performance, distributed memory object PHP Caching mechanism system is used to reduce database load and improve access speed in dynamic applications.
PHP’s buffer:
There are eaccelerator, apc, phpa, xcache, I won’t talk about these, just search a bunch of them and see for yourself , it’s OK to know that this thing exists
MYSQL cache:
This is also considered non-code level. Classic databases use this method. See the operation below. Time, 0.09xxx and the like
I’ll post a section of my.ini modified by the guy in blue. The 2G MYISAM table can be around 0.05S. It is said that he changed it for almost a year
Web cache based on reverse proxy:
such as Nginx, SQUID, mod_proxy (apache2 and above are divided into mod_proxy and mod_cache)
Example of NGINX
DNS polling:
BIND is an open source DNS server software. This is a big deal to mention. Just search it yourself. Everyone knows that this thing exists.
I know that some big websites such as chinacache do this. To put it simply, it is multi-server. The same page or file is cached on different servers and automatically parsed to the relevant servers according to the north and south.