How to use gettext to achieve internationalization in PHP?

DEMO project structure

Problem Description

When I set the value of the variable $lang to zh_CN, the text corresponding to zh.CN.mo in the zh_CN folder can be displayed normally, but when I change the value of $lang to ja_JP or en_US, the page will be output as is,

But when I move the ja_JP under the ja_JP.mo folder to the zh_CN folder and rename it to zh_CN.mo, I set the value of the variable $lang to zh_CN and the Japanese text can be displayed normally. , why?

Reply content:

DEMO project structure

Problem Description

When I set the value of the variable $lang to zh_CN, the text corresponding to zh.CN.mo in the zh_CN folder can be displayed normally, but when I change the value of $lang to ja_JP or en_US, the page will be output as is,

But when I move the ja_JP under the ja_JP.mo folder to the zh_CN folder and rename it to zh_CN.mo, I set the value of the variable $lang to zh_CN and the Japanese text can be displayed normally. , why?

It runs normally under Linux and does not display translation under Windows environment

The specific reason is unknown