获取PHP中的类的所有实例 [英] Get all instances of a class in PHP

问题描述

我想获得某个类的对象的所有实例。

例如：

  class Foo {
} 
 
 $ a = new Foo（）; 
 $ b = new Foo（）; 
 
 $ instances = get_instances_of_class（'Foo'）; 
  

$ instances 应为 array（$ a，$ b）或数组（$ b，$ a） >

A plus是如果函数返回具有所请求类的超类的实例，但这不是必需的。

我可以想到的一种方法是使用一个静态类成员变量，它保存一个实例数组。在类的构造函数和析构函数中，我将从数组中添加或删除 $ this 。

解决方案

如果你从所有的对象中派生所有的对象，那么这是非常麻烦和容易出错的。一个TrackableObject类，这个类可以设置为处理这样​​的事情（只要确保你调用 parent :: __ construct（）和 parent :: __ destruct （）。

  class TrackableObject 
 {
 protected static $ _instances = array（）; 
 
 public function __construct（）
 {
 self :: $ _ instances [] = $ this; 
} 
 
 public function __destruct（）
 {
 unset（self :: $ _ instances [array_search（$ this，self :: $ _ instances，true）]）; 
} 
 
 / ** 
 * @param $ includeSubclasses可选地，在返回集中包含子类
 * @returns对象的数组数组
 * / 
 public static function getInstances $ includeSubclasses = false）
 {
 $ return = array（）; 
 foreach（self :: $ _ instances as $ instance）{
 if（$ instance instanceof get_class（$ this））{
 if（$ includeSubclasses ||（get_class（$ instance）== = get_class（$ this））{
 $ return [] = $ instance; 
} 
} 
} 
 return $ return; 
} 
} 
  

这个的主要问题是没有对象会被垃圾回收作为它的引用仍然存在于 TrackableObject :: $ _ instances ）中，因此需要调用 __ destruct（）手动破坏所述对象（在PHP 5.3中添加了循环引用垃圾回收，可能会提供额外的垃圾回收机会）

I would like to get all the instances of an object of a certain class.

For example:

class Foo {
}

$a = new Foo();
$b = new Foo();

$instances = get_instances_of_class('Foo');

$instances should be either array($a, $b) or array($b, $a) (order does not matter).

A plus is if the function would return instances which have a superclass of the requested class, though this isn't necessary.

One method I can think of is using a static class member variable which holds an array of instances. In the class's constructor and destructor, I would add or remove $this from the array. This is rather troublesome and error-prone if I have to do it on many classes.

解决方案

If you derive all your objects from a TrackableObject class, this class could be set up to handle such things (just be sure you call parent::__construct() and parent::__destruct() when overloading those in subclasses.

class TrackableObject
{
    protected static $_instances = array();

    public function __construct()
    {
        self::$_instances[] = $this;
    }

    public function __destruct()
    {
        unset(self::$_instances[array_search($this, self::$_instances, true)]);
    }

    /**
     * @param $includeSubclasses Optionally include subclasses in returned set
     * @returns array array of objects
     */
    public static function getInstances($includeSubclasses = false)
    {
        $return = array();
        foreach(self::$_instances as $instance) {
            if ($instance instanceof get_class($this)) {
                if ($includeSubclasses || (get_class($instance) === get_class($this)) {
                    $return[] = $instance;
                }
            }
        }
        return $return;
    }
}

The major issue with this is that no object would be automatically picked up by garbage collection (as a reference to it still exists within TrackableObject::$_instances), so __destruct() would need to be called manually to destroy said object. (Circular Reference Garbage Collection was added in PHP 5.3 and may present additional garbage collection opportunities)

这篇关于获取PHP中的类的所有实例的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！