Grazie mille, ho risolto
Posto il codice che ho usato nel caso a qualcuno potesse servire
class plgContentGalleria extends JPlugin
{
private $limit;
function plgContentGalleria( &$subject, $params )
{
parent::__construct( $subject, $params );
$this->limit = $this->params->get('limit', 3);
if (!is_numeric($limit) || $limit < 0) $limit = 3;
}
function onPrepareContent( &$article, &$params, $limitstart ) {
if (JRequest::getString('view', 'article') == 'article')
return false;
$regex = "#{gallery}(.*?){/gallery}#s";
$article->text = preg_replace_callback($regex,array($this,"sostituisci"), $article->text);
return true;
}
private function sostituisci($matches) {
if (preg_match('#limit_quantity=#', $matches[1]))
return '{gallery}'.$matches[1].'{/gallery}';
else
return '{gallery}'.$matches[1].',limit_quantity='.$this->limit.'{/gallery}';
}
}