ajax+php no refresh post and registration check

The two ajax+php non-refresh examples are non-refresh reply and registration check. The function of non-refresh reply is already very common in many forums or technical blogs. The experience when replying is very good. All previous replies have been It is to go to another page for processing, then post back, and reload the page, which gives the user a very bad experience. Posting without refreshing actually uses a combination of ajax and php to write to the database. The other is registration verification. When we register a user on Baidu or NetEase, or when registering on this blog 04ie.com, you will be prompted without refreshing whether your user name already exists in the database. If it exists, it will be directly displayed on this page. Tip, if it does not exist, register it. This kind of application is very widespread. Mature systems on the Internet have basically implemented non-refresh registration verification. The above are complete examples, with actual database files attached. The specific principles will not be introduced. The examples are very simple. If you want to use such a function, just extract it and integrate it.