code: public function encrypt($data)
      {
          $cipher = $box[] = $key[] = '';
  
          $pwd_length = strlen($this->key);
          $data_length = strlen($data);
  
          for ($i = 0; $i < 256; $i++) {
              $key[$i] = ord($this->key[$i % $pwd_length]);
              $box[$i] = $i;
          }
  
          for ($j = $i = 0; $i < 256; $i++) {
              $j = ($j + $box[$i] + $key[$i]) % 256;
              $tmp = $box[$i];
              $box[$i] = $box[$j];
              $box[$j] = $tmp;
          }
  
          for ($a = $j = $i = 0; $i < $data_length; $i++) {
              $a = ($a + 1) % 256;
              $j = ($j + $box[$a]) % 256;
  
              $tmp = $box[$a];
              $box[$a] = $box[$j];
              $box[$j] = $tmp;
  
              $k = $box[(($box[$a] + $box[$j]) % 256)];
              $cipher .= chr(ord($data[$i]) ^ $k);
          }
  
          return strtoupper(StrUtil::String2Hex($cipher));
      }
docs: rc4加密算法
  @param $data
  @return string
  @throws \Exception