(PECL ds >= 1.0.0)
Ds\Set::intersect — Creates a new set by intersecting values with another set
    Creates a new set using values common to both the current instance and another set.
    In other words, returns a copy of the current instance with all values removed that
    are not in the other set.
  
    A ∩ B = {x : x ∈ A ∧ x ∈ B}
  
setThe other set.
    The intersection of the current instance and another set.
    
Example #1 Ds\Set::intersect() example
<?php
$a = new \Ds\Set([1, 2, 3]);
$b = new \Ds\Set([3, 4, 5]);
var_dump($a->intersect($b));
?>
The above example will output something similar to:
object(Ds\Set)#3 (1) {
  [0]=>
  int(3)
}
