Summarize the various methods of PHP caching technology

Summary of various methods of PHP caching technology

The data caching mentioned here refers to the database query PHP caching mechanism. Every time a page is accessed, it will first detect whether the corresponding cached data exists. If it does not exist, connect to the database. Obtain the data and serialize the query results and save them to the file. In the future, the same query results will be obtained directly from the cache table or file.

1. Universal caching technology:

Data caching: The data caching mentioned here refers to the database query PHP caching mechanism. Every time a page is accessed, it will first detect whether the corresponding cached data exists. If it does not exist, connect to it. The database obtains the data and serializes the query results and saves them to the file. In the future, the same query results are obtained directly from the cache table or file. 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, the contents in the attached table are generated into an array and saved in a field of the main table. The editor of Brothers in Arms reminds: decompose the array when needed. 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.

2. Page caching:

Every time you access a page, it will first detect whether the corresponding cached page file exists. If it does not exist, connect to the database, get the data, display the page and generate a cached page file at the same time, so that next time The page file comes into play when accessed. (Template engines and some common PHP caching mechanism classes on the Internet usually have this function)

3. 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 If the expiration timestamp is subtracted, then the cache is used, otherwise the cache is updated.

4. Content-triggered caching:

When data is inserted or updated, the PHP cache mechanism is forced to be updated.

5. Static caching:

The static caching mentioned here refers to static caching, which directly generates text files such as HTML or XML and regenerates them when there are updates. It is suitable for pages that do not change much. I will not talk about it here. .

The above content is a code-level solution. The following content is a server-side caching solution. It is not code-level and requires the cooperation of multiple parties to achieve it.

6. Memory cache:

Memcached is high-performance and distributed The in-memory object PHP caching mechanism system is used to reduce database load and improve access speed in dynamic applications.

7. PHP's buffer:

There are eaccelerator, apc, phpa, xcache, I won't talk about these. Search a bunch of them and see for yourself. If you know this thing, it's OK.

8. MYSQL Cache:

This is also considered non-code level. Classic databases use this method. Look at the running time below, 0.09xxx and the like

9. Web cache based on reverse proxy:

such as Nginx, SQUID, mod_proxy (apache2 and above are divided into mod_proxy and mod_cache)

10. DNS polling:

BIND is an open source DNS server software. This is a big deal to mention. Search it yourself. Everyone knows this Just stuff.
I know that some large websites 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 server according to the north and south.