Let’s talk about the solution to PHP cache file writing failure

Recently, I encountered a very annoying problem when using a PHP script to create cache files. I found that the cache file was not being written as expected, but instead giving me some weird errors.

After some investigation and analysis, I finally found a solution to this problem. In this article, I will share with you the process of solving this problem, hoping to be helpful to developers who use PHP for file caching.

Question

In my PHP application, I use a script to create cache files. The basic process of this script is:

1. Check whether the cache file already exists, and if it exists, read the data in the file.
2. If the cache file does not exist or has expired, then I need to regenerate and write the cache data.
3. Write new data to the cache file and save it.

But in my test, I found that the save operation was not successful. I tried multiple times, but each time the cache file created was blank with no data.

So I checked my code carefully, but didn't find any problems. I even tried creating the cache file using different filenames and paths, but the result was the same, the save operation didn't succeed.

Solution

Finally, I discovered that there was a small error in my code. When I write data to a file, I use the PHP function file_put_contents(). But I ignored an important parameter of this function - FILE_APPEND.

If FILE_APPEND is set to true, new data will be appended to the end of the file instead of overwriting the original data. That's why my cache file is always blank.

Therefore, the correct code for writing data should be:

file_put_contents($cache_file_name, $data, LOCK_EX | FILE_APPEND);

In this way, by setting the FILE_APPEND parameter to true, I can append data instead of overwriting it.

Conclusion

When using PHP for file caching, you must pay attention to the method and parameters of writing data. This small detail can have serious consequences for your application.

Although PHP is a very powerful and flexible language, any of us programmers can make mistakes. Only through continuous learning and practice can we avoid such mistakes and continuously improve our skills during the development process.

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