(PECL ds >= 1.0.0)
Ds\Set::diff — Creates a new set using values that aren't in another set
$set
   ) : Ds\SetCreates a new set using values that aren't in another set.
    A \ B = {x ∈ A | x ∉ B}
  
setSet containing the values to exclude.
    A new set containing all values that were not in the other set.
  
Example #1 Ds\Set::diff() example
<?php
$a = new \Ds\Set([1, 2, 3]);
$b = new \Ds\Set([3, 4, 5]);
var_dump($a->diff($b));
?>
以上例程的输出类似于:
object(Ds\Set)#3 (2) {
  [0]=>
  int(1)
  [1]=>
  int(2)
}