PHP マニュアル: Creates a new set using values from the current instance and another set

public Ds\Set Ds\Set::union(Ds\Set $set)

Creates a new set that contains the values of the current instance as well as the values of another set.

A ∪ B = {x: x ∈ A ∨ x ∈ B}

A new set containing all the values of the current instance as well as another set.

例1 Ds\Set::union example

<?php
$a = new \Ds\Set([1, 2, 3]);
$b = new \Ds\Set([3, 4, 5]);

var_dump($a->union($b));
?>

上の例の出力は、たとえば以下のようになります。

object(Ds\Set)#3 (5) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
  [3]=>
  int(4)
  [4]=>
  int(5)
}