PHP mb_ Substr Chinese garbled code

After testing

$sheng=mb_substr(' Zhejiang Province ',0,2);
// The result is garbled 

because mb_substr() Function in use , You need to specify the code in the following parameters . Don't specify . By default, Chinese is regarded as three characters . If specified , Treat Chinese as a character , therefore

$sheng=mb_substr(' Zhejiang Province ',0,2,"utf-8");
// The result is Zhejiang