/**
  * Output the object as HTML <meta> elements
  * @return string HTML meta element string
  */
 public function toHTML()
 {
     return rtrim(OpenGraphProtocol::buildHTML(get_object_vars($this), static::PREFIX), PHP_EOL);
 }
 /**
  * Output the object as HTML <meta> elements
  *
  * @param string $encoding
  *
  * @return string HTML meta element string
  */
 public function toHTML($encoding = 'UTF-8')
 {
     return rtrim(OpenGraphProtocol::buildHTML(get_object_vars($this), static::PREFIX, $encoding), PHP_EOL);
 }