union method will add the
$items value to a copy of the existing collection. If there are key collisions between the collection instance and the provided
$items, the elements from the collection instance will be used instead.
union method does not modify the collection instance it was invoked on; instead, it will return a copy of the original collection with the provided
$items added to it.
public function union( $items );
The following example demonstrates both the basic use of the
union method as well as it's behavior when it encounters conflicting keys:
$collection = collect([ 'firstName' => 'Johnathon', 'lastName' => 'Koster', 'age' => 27 ])->union([ 'firstName' => null, 'lastName' => null, 'age' => 18, 'city' => 'Mayville' ]);
After the above code has executed, the
$collection collection instance would contain the following values: