How can php not generate cache?

In web development, caching is often a headache. Although caching can improve the access speed and performance of the website, sometimes we hope to not use caching and re-obtain the data with each request to ensure the timeliness and accuracy of the data. In Php, there are many methods to achieve the effect of not generating cache. This article will introduce these methods in detail.

1. Set Header header information

In Php, you can control caching by setting Header header information. The following code demonstrates how to set the Header header information to disable caching:

<?php
  header("Expires: Tue, 26 Jul 1970 05:00:00 GMT");
  header("Cache-Control: no-cache, must-revalidate");
  header("Pragma: no-cache");
?>

In the above code, the Expires field is set to a past time, so that the browser will think that the page has expired and will not cache it; Cache-Control Both the field and the Pragma field are set to no-cache so that the browser will not cache the page. After setting the Header header information, the data will be re-obtained for each request instead of reading the data from the cache.

2. Use the session_cache_limiter function

The session_cache_limiter function is a function that comes with Php and can be used to control the cache. The following code demonstrates how to use the session_cache_limiter function to disable caching:

<?php
  session_cache_limiter("nocache");
  session_start();
?>

In the above code, the session_cache_limiter("nocache") function is called, which means that the browser is prohibited from caching this page. Using the session_cache_limiter function, all output will be prohibited from caching, including content output through the echo function.

3. Disable OPcache module

OPcache is an accelerator module officially provided by Php, which can cache compiled code to improve performance. But sometimes we want to be able to disable OPcache to ensure that the code is re-executed on every request to get the latest results. The following code demonstrates how to disable the OPcache module:

<?php
  ini_set("opcache.enable", 0);
?>

In the above code, the ini_set("opcache.enable", 0) function is called, indicating that the OPcache module is disabled. Using this method ensures that the code is re-executed on every request.

4. Avoid using ETag

ETag is an identifier used in the HTTP protocol to determine whether a resource has been modified. When a browser requests a resource, the server generates an ETag based on the content of the resource and then sends it to the browser. When the same resource is requested next time, the browser will send the ETag obtained last time to the server, and the server will use this ETag to determine whether the resource has been modified. If the resource has not been modified, a 304 Not Modified status code will be returned, and the browser will obtain the resource from the cache. In order to avoid caching, we can avoid using ETag. Here is an example:

<?php
  header("ETag: ");
?>

In the above code, set the ETag to an empty string so that the server cannot determine the resource every time the browser requests the same resource. Whether it has been modified, the content of the resource will be returned directly instead of returning the 304 Not Modified status code. This ensures that the resource is re-fetched on every request.

5. Delete cache

In addition to the above methods, another feasible method is to delete the cache. You can use the unlink function to delete files in Php. The following is an example:

<?php
  $filename = "cache.txt";
  if(file_exists($filename)){
    unlink($filename);
  }
?>

In the above code, use the unlink function to delete the file cache.txt. When you need to delete the cache, you can use this method to delete the cache files.

Summary

In web development, caching is an important consideration. Although caching can effectively improve website performance, sometimes we want to be able to disable caching to ensure the timeliness and accuracy of data. This article introduces five methods to disable caching in Php, including setting Header header information, using the session_cache_limiter function, disabling the OPcache module, avoiding the use of ETag, and deleting the cache. Using the above method can effectively control the cache of the page and ensure that the data is re-fetched on every request.

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