/**
* Get the keys of the array.
*
* @param boolean $recursive
* (optional) TRUE to get keys of array elements that are also arrays.
*
* @return NodeCollection
*/
public function getKeys($recursive = TRUE)
{
$keys = new NodeCollection();
$index = 0;
foreach ($this->elements->getItems() as $element) {
if ($element instanceof ArrayPairNode) {
$keys->add($element->getKey());
$value = $element->getValue();
} else {
$keys->add(Token::integer($index++));
$value = $element;
}
if ($recursive && $value instanceof ArrayNode) {
$keys->add($value->getKeys($recursive));
}
}
return $keys;
}