Simplified conversion in the UTF8 Character Set and simplified conversion in the utf8 Character Set

Simplified conversion in the UTF8 Character Set and simplified conversion in the utf8 Character Set

After searching for the UTF8 character set on the Internet for a long time, I have not found the simplified conversion in the UTF8 character set. Maybe someone has written such code on the Internet.
I once found a JS version, but it cannot be used in UTF8 encoding, so I came up with the idea of writing it myself.
In fact, the implementation principle of this code is very simple. It is just a process of replacing character sets. I believe most people can write it out.
The following is the code. I don't know if there are any bugs. If you have any problems in usage, you can ask

Http://php.662p.com/thread-565-1-1.html