$new_term = array(
    'vid' => 1,
    'name' => 'someterm',

);
$new_term = (object) $new_term;
taxonomy_term_save($new_term);
$pippo = taxonomy_get_term_by_name("$v");
$pippo_keys = array_keys($pippo);
$node->field_tags[$node->language][]['tid'] = $pippo_keys[0];