(PHP 8 >= 8.4.0)
mb_lcfirst — Make a string's first character lowercase
   Performs a multi-byte safe lcfirst() operation,
   and returns a string with the first character of
   string lowercased.
  
stringencodingencoding
参数为字符编码。如果省略或是 null,则使用内部字符编码。
Returns the resulting string.
