A sequence which will be concatenated with this Linq object.
return
Linq
A new Linq object that contains the concatenated elements of the input sequence and the original Linq sequence.
public function concat($second)
{
LinqHelper::assertArgumentIsIterable($second, "second");
$allItems = new \ArrayIterator([$this->iterator, $second]);
return new Linq(new SelectManyIterator($allItems));
}