How to update an article

$program = new mxProgram;
$program->getBy(array('id' => $programCodeOrID, 'code' => array($programCodeOrID, '=', 'OR')));
$article = $program->getArticle($recId);
$article->fieldname1 = $value1;
$article->fieldname2 = $value2;
$articleupdate = $article->update();