PHP SplObjectStorage使用实例

PHP SPL SplObjectStorage是用来存储一组对象的，特别是当你需要唯一标识对象的时候。
PHP SPL SplObjectStorage类实现了Countable,Iterator,Serializable,ArrayAccess四个接口。可实现统计、迭代、序列化、数组式访问等功能。

看下面一个简单的例子：

    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();
    }