code: public static function paraFilter($para)
      {
          $paraFilter = [];
          foreach ($para as $key => $val) {
              if ($val === '' || $val === null) {
                  continue;
              } else {
                  if (!is_array($para[$key])) {
                      $para[$key] = is_bool($para[$key]) ? $para[$key] : trim($para[$key]);
                  }
  
                  $paraFilter[$key] = $para[$key];
              }
          }
  
          return $paraFilter;
      }
docs: 移除空值的key
  @param $para
  @return array
  @author helei