class A {
  public $i;
  public function __construct($i) {
    $this->i = $i;
  }
}
 
$a1 = new A(1);
$a2 = new A(2);
$a3 = new A(3);
$a4 = new A(4);
 
$container = new SplObjectStorage();
 
//SplObjectStorage::attach 添加对象到Storage中
$container->attach($a1);
$container->attach($a2);
$container->attach($a3);
 
//SplObjectStorage::detach 将对象从Storage中移除
$container->detach($a2);
 
//SplObjectStorage::contains用于检查对象是否存在Storage中
var_dump($container->contains($a1)); //true
var_dump($container->contains($a4)); //false
 
//遍历
$container->rewind();
while($container->valid()) {
  var_dump($container->current());
  $container->next();
}