$user_name= ‘张三’;
$strlen= mb_strlen($user_name,'utf-8');
if($strlen>=2){
$firstStr= mb_substr($user_name,0,1,'utf-8');
$lastStr= mb_substr($user_name,-1,1,'utf-8');
$user_name=$strlen==2?$firstStr. str_repeat('*',mb_strlen($user_name,'utf-8') -1) :$firstStr. str_repeat("*",$strlen-2) .$lastStr;
}
