code: public function clear($name = null)
      {
          if (!is_null($name)) {
              $name = strtolower($name);
              if (array_key_exists($name, self::$clearings)) {
                  $this->{$name} = self::$clearings[$self::$clearings];
              }
          } else {
              foreach (self::$clearings as $n=>$v) {
                  $this->{$n} = $v;
              }
          }
          return $this;
      }
docs: Global variable clearer
  
  @param string $name
  @return self