PHP putenv function Chinese cannot use the problem

If you know laravel can look at the above piece, if you do not know, go straight to the dividing line below;

Any of the Env items here take mail_driver as an example
Change to "my" with the ENV function can get to the value of normal;
Instead of "I" with the ENV function can not be obtained normally;

MAIL_DRIVER=我var_dump(env(MAIL_DRIVER''));  // NULLMAIL_DRIVER=我的var_dump(env(MAIL_DRIVER''));  // 我的

Some other Chinese such as "good" will also appear this situation;
Have to say, laravel and profound; study the ENV function source code;
The last problem to locate is;
-------------------------------------------------understand and don't understand the split line of the Laravel frame------------------------------------------------

putenv("PROJECT_NAME=我的");phpinfo();

Environment in phpinfo can be searched for project_name

putenv("PROJECT_NAME=我");phpinfo();

Environment in phpinfo can not be searched project_name

Ask the parents, why is this? How to set the Chinese value without obstacles?

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