update some info

src/StringHelper.php

@@ -146,6 +146,18 @@ public static function strlen(string $str, string $encoding = 'UTF-8'): int
         return \function_exists('mb_strlen') ? \mb_strlen($str, $encoding) : \strlen($str);
     }
 
+    /**
+     * @param string $string
+     * @return int
+     */
+    public static function utf8Len(string $string): int
+    {
+        // strlen: one chinese is 3 char.
+        // mb_strlen: one chinese is 1 char.
+        // mb_strwidth: one chinese is 2 char.
+        return \mb_strlen($string, 'utf-8');
+    }
+
     /**
      * 计算字符长度
      * @param  string $str