Add a literal value as a property of the resource
The value can either be a single value or an array of values.
Example: $resource->add('dc:title', 'Title of Page');
mixed $property The property name:
mixed $values The value or values for the property:
string $lang The language of the literal:
integer The number of values added
public function addLiteral($property, $values, $lang = null) {
$this
->checkHasGraph();
return $this->graph
->addLiteral($this->uri, $property, $values, $lang);
}