What is cache? How to automatically clear cache in php?

During the development process of PHP projects, some cache usage situations often occur, such as website cache, database cache, etc. Caching can improve the response speed of the website, but if the cache is used incorrectly, it will cause some abnormal errors in the program. In order to solve these problems, program developers usually need to take advantage of some functions of PHP to automatically clear the cache.

1. What is cache?

Caching is a technology for optimizing computer resources. When we need to access some underlying resources (such as databases) or more time-consuming operations (such as reading complex pages), we can first write the results into the cache, and the next time we need to obtain the results, we The cache can be accessed directly, significantly increasing access speed.

For example, we can use PHP's built-in caching mechanism to cache some frequently used variables or function results into memory. These variables or function results can be read more quickly the next time they are used.

2. Details of caching usage

The caching mechanism will greatly improve our operating efficiency, but we must pay attention to the following details.

1. Correct timing

The cache mechanism needs to be used at the right time, neither too early nor too late.

If used too early, data inconsistency may occur because the data may not have been updated. If used too late, it may not reduce the amount of computation in the effective time.

2. Cache expiration time

When adding a cache, you need to specify the cache expiration time. Usually, the cache life cycle needs to be determined based on specific business needs. If the data we cache needs to be updated frequently, then the cache lifespan should be correspondingly shorter to facilitate timely updates.

3. Cache Optimization

If our cache is used incorrectly and the logic of the cached results is not consistent with the query results, it may affect the stability and performance of the program.

In order to avoid the above problems, we need to consider the following aspects:

① Ensure the correctness of the data source and avoid the problem of cached data expiring and not being updated;

② Reduce the scope of the cache to avoid performance problems caused by too large a cache;

③ Use a cluster of cache systems to adapt to scenarios with large amounts of data.

3. How to automatically clear the cache

In the above cache usage details, we mentioned the cache expiration time. In actual development, in order to maintain the accuracy of the cache, we usually need to automatically clear the cache within a certain time range.

In order to achieve this function, we can clear the cache through PHP's timer. In PHP, we can use cron to set up scheduled tasks. Simply put, cron is a time-based job scheduler.

Taking the Linux system as an example, we can use cron to run a script at a specified time point and implement the function of automatically clearing the cache in the script. Below is an example script that automatically clears cache.

<?php  
  // 加载缓存库
  require_once("cache.php"); 
  // 清除缓存
  Cache::clear(); 
?>

We can save the above script to our own Linux server, and then set it to run every 2 minutes. In this way, the cache will be automatically cleared every 2 minutes to ensure the stability and performance of the program.

4. Summary

The caching mechanism is a very important part of PHP project development, which can significantly improve the response speed and performance of our program. However, when using cache, we often need to pay attention to some cache usage details to avoid some problems.

In this article, we explain the basic concepts of caching and the details of caching. At the same time, we also introduced how to automatically clear the cache through a timer to ensure the correctness and stability of the cache. I hope this article can be helpful to you, thank you for reading!

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