How to solve the problem that updated pictures cannot be displayed in PHP

In the process of using PHP to develop web applications, sometimes you encounter the problem of updating images but failing to display them. This problem is usually caused by cache issues. The following will introduce in detail how to solve the problem that the updated image cannot be displayed in PHP.

1. Problem description

During the development process, sometimes we need to replace the original picture, but even if the path and name of the picture are updated, the new picture will not be successfully displayed and will still be displayed. Original picture.

2. Cause of the problem

This problem is generally caused by two reasons: browser cache and server cache.

1. Browser Cache

When the browser accesses a web page, static resources such as images will be cached in the local hard disk to improve the web page access speed. If an image is updated but the image in the cache is not updated, the browser will continue to display the old image in the cache.

2. Server Cache

If the cache mechanism is used, the cache needs to be cleared when updating the image, otherwise it will not take effect even if the image is updated.

3. Solution

We can adopt different solutions for different reasons.

1. Browser cache

After updating the image, we need to clear the browser cache first. Different browsers have different methods for clearing cache, for example:

• Chrome browser: Press ctrl shift delete to open the clear browsing data interface, and select "from the initial time" or "from one week ago" to start clearing;
• Firefox browser: Press ctrl shift delete to open the clear history interface, select "All History" and check the "Cache" option;
• Edge browser: Press ctrl shift delete to open the clear history Browse the data interface and select "Start from the Beginning" or "Start from One Week Ago" to start clearing.

After clearing the cache and refreshing the web page, the updated image will be displayed.

2. Server cache

For server cache, we need to understand what type of cache the website uses, and then clear it accordingly. There are three general cache types:

• File cache: cache the data in a file, and the cache file needs to be deleted when updating the data;
• Database cache: cache the data in the database, When updating data, you need to clear the cache table in the database;
• Memory cache: cache the data in memory, and you need to clear the cache when updating data.

We need to understand and clear the corresponding cache according to the specific conditions of the website to solve this problem.

4. Summary

The updated image cannot be displayed, usually due to cache problems. We need to clear the browser cache and server cache to resolve this issue. The specific method needs to be cleared according to the cache type. In order to avoid this problem, we need to consider the caching mechanism during development, and be sure to clear the cache at the same time when updating static resources such as images.

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