Summary of PHP caching technology methods and common problems

PHP caching technology methods and summary of common problems

As the number of visits to the website continues to increase, caching technology is particularly important in order to improve the response speed and performance of the website. In PHP development, caching technology also plays a vital role. This article will introduce methods of PHP caching technology and solutions to common problems.

1. PHP caching technology method

1. File caching

File caching refers to caching data in a file and reading the file directly when needed. The specific implementation method is to serialize the data and store it in the file, and then deserialize it when reading. File caching is relatively simple and easy to implement, but under high concurrency situations, file locking problems may occur, reducing its performance.

2.Redis Cache

Redis is an open source NoSQL database. It supports a variety of data structures (such as String, List, Hash, Set, etc.), and its reading and writing speed is very fast. The implementation of Redis cache is to use Redis API functions to cache data in the Redis server and set the cache time and expiration time. Redis cache is fast and efficient, and can be distributed in the cluster. It has natural support for distributed locks, solving the file lock problem.

3.Memcached cache

Memcached is a high-performance distributed memory cache system, which is used by well-known companies such as Tencent QQ and Sina Weibo. Memcached caching is also implemented through API functions, caching a large amount of data into memory, and the cache timeliness is similar to that of Redis. Compared with file caching, Memcached caching is faster, more efficient, more stable and secure, and does not cause file lock problems.

4.OPcache

OPcache is a PHP accelerator that can cache bytecode and avoid repeated parsing and compilation of PHP scripts, thus improving the operating efficiency of PHP. OPcache takes up less memory and can improve page response speed. Its disadvantage is that it cannot distribute caching and cannot reduce application startup time.

2. Solutions to common problems with PHP caching

1. Unable to clear the cache

Clearing the cache often causes problems. If the clearing fails, the data on the accessed page may not be the latest. The data. At this time, you need to pay attention to the expiration time of the cache and whether the cache is occupied. In addition, some caching systems provide command line tools or web interfaces to easily clear the cache.

2. Cache breakdown

Cache breakdown means that there is no data that needs to be queried in the cache, but these data exist in the database, causing the request to reach the database directly. In this case, a mutex lock needs to be added to ensure that when obtaining unqueried data, only one request accesses the database, and other requests are waiting.

3. Cache avalanche

Cache avalanche means that when the expiration time is close, a large amount of cached data becomes invalid at the same time, causing requests to go directly to the database and affecting system performance. At this time, a certain random time can be added to the cache expiration time to stagger the cache expiration time, thereby avoiding simultaneous failures and ensuring system performance.

4. Cache penetration

Cache penetration refers to querying data that is not in the cache or database, which is a malicious attack. This can be solved by techniques such as Bloom filters. Bloom filter is a method to quickly determine whether an element exists in a collection. It can determine whether a query has results. If there are no results, it can directly return an error message.

Through the above methods, the performance and response speed of PHP applications can be improved, thereby becoming efficient web applications.

The above is the detailed content of Summary of PHP caching technology methods and common problems. For more information, please follow other related articles on the PHP Chinese website!