PHP:检测变量值何时更改

Question

我想知道是否有办法向变量添加类似更改侦听器的内容.我所说的最简单的例子就是沿着这些方向发挥作用;

// Start with a variable
$variable = "some value";

// Define a listener
function myChangeListener($variable) {
    // encode with json_encode and send in cookie
}

// Add my listener to the variable
addListenerToVariable(&$variable, 'myChangeListener');

// Change the variables value, triggering my listener
$variable = "new value";

现在你可能会问为什么在世界上我甚至需要打扰这种方法,为什么不只是创建一个函数来设置cookie.答案是我有一个&__get($var)魔术方法返回对多维数组元素的引用,我希望使用这样的东西来检测数组元素或其中一个子元素是否已被编辑,然后发送一个cookie,如果有的话.希望的结果会像这样起作用;

$cookies->testArray["test"] = "newValue";
// This would send the cookie 'testArray' with the value '{"test":"newValue"}'

老实说,我认为这是完全不可能的,如果我是正确的,我道歉.但我昨天刚刚学会了如何正确使用引用,所以我想在完全注销这个想法之前我会问.

感谢我得到的任何回复,无论是我希望的还是我期望的.

编辑:

为了更加清晰,这里是我想要完成的一个示例类;

class MyCookies {
    private $cookies = array();
    private $cookieTag = "MyTag";

    public function __construct() {
        foreach($_COOKIE as $cookie => $value) {
            if(strlen($cookie)>strlen($this->cookieTag."_")&&substr($cookie,0,strlen($this->cookieTag."_"))==$this->cookieTag."_") {
                $cookieVar = substr($cookie,strlen($this->cookieTag."_"));
                $this->cookies[$cookieVar]['value'] = json_decode($value);
            }
        }
    }

    // This works great for $cookies->testArray = array("testKey" => "testValue");
    // but never gets called when you do $cookies->testArray['testKey'] = "testValue";
    public function __set($var, $value) {
        if(isset($value)) {
            $this->cookies[$var]['value'] = $value;
            setcookie($this->cookieTag.'_'.$var,json_encode($value),(isset($this->cookies[$var]['expires'])?$this->cookies[$var]['expires']:(time()+2592000)),'/','');
        } else {
            unset($this->cookies[$var]);
            setcookie($this->cookieTag.'_'.$var,'',(time()-(172800)),'/','');
        }
        return $value;
    }

    // This gets called when you do $cookies->testArray['testKey'] = "testValue";
    public function &__get($var) {
        // I want to add a variable change listener here, that gets triggered
        // when the references value has been changed.

        // addListener(&$this->config[$var]['value'], array(&$this, 'changeListener'));

        return $this->config[$var]['value'];
    }

    /*
    public function changeListener(&$reference) {
        // scan $this->cookies, find the variable that $reference is the reference to (don't know how to do that ether)
        // send cookie
    }
    */

    public function __isset($var) {
        return isset($this->cookies[$var]);
    }

    public function __unset($var) {
        unset($this->cookies[$var]);
        setcookie($this->cookieTag.'_'.$var,'',(time()-(172800)),'/','');
    }

    public function setCookieExpire($var, $value, $expire=null) {
        if(!isset($expire)) {
            $expire = $value;
            $value = null;
        }
        if($expire<time()) $expire = time() + $expire;
        if(isset($value)) $this->cookies[$var]['value'] = $value;
        $this->cookies[$var]['expires'] = $expire;
        setcookie($this->cookieTag.'_'.$var,json_encode((isset($value)?$value:(isset($this->cookies[$var]['value'])?$this->cookies[$var]['value']:''))),$expire,'/','');
    }
}

至于为什么我不想拥有更新功能,这只是个人偏好.这将在其他人可以扩展的框架中使用,我认为让他们能够将cookie视为单行代码中的变量感觉更加光滑.

Answer 1

如果您想在数组或其他任何内容中实现自己的事件处理程序/触发器，那么您可以使用类包装器。

正如您所注意到的，对于一个变量 __get()和__set()魔术方法就足够了。对于数组有一个更好的处理程序：ArrayAccess。它允许使用类方法和常见数组语义（如某些其他语言中的集合）来模拟数组操作。

<?php
header('Content-Type: text/plain');

// ArrayAccess for Array events
class TriggerableArray implements ArrayAccess {
    protected $array;      // container for elements
    protected $triggers;   // callables to actions

    public function __construct(){
        $this->array    = array();

        // predefined actions, which are availible for this class:
        $this->triggers = array(
            'get'    => null,     // when get element value
            'set'    => null,     // when set existing element's value
            'add'    => null,     // when add new element
            'exists' => null,     // when check element with isset()
            'unset'  => null      // when remove element with unset()
        );
    }

    public function __destruct(){
        unset($this->array, $this->triggers);
    }

    public function offsetGet($offset){
        $result = isset($this->array[$offset]) ? $this->array[$offset] : null;

        // fire "get" trigger
        $this->trigger('get', $offset, $result);

        return $result;
    }

    public function offsetSet($offset, $value){
        // if no offset provided
        if(is_null($offset)){
            // fire "add" trigger
            $this->trigger('add', $offset, $value);

            // add element
            $this->array[] = $value;
        } else {
            // if offset exists, then it is changing, else it is new offset
            $trigger = isset($this->array[$offset]) ? 'set' : 'add';

            // fire trigger ("set" or "add")
            $this->trigger($trigger, $offset, $value);

            // add or change element
            $this->array[$offset] = $value;
        }
    }

    public function offsetExists($offset){
        // fire "exists" trigger
        $this->trigger('exists', $offset);

        // return value
        return isset($this->array[$offset]);
    }

    public function offsetUnset($offset){
        // fire "unset" trigger
        $this->trigger('unset', $offset);

        // unset element
        unset($this->array[$offset]);
    }

    public function addTrigger($trigger, $handler){
        // if action is not availible and not proper handler provided then quit
        if(!(array_key_exists($trigger, $this->triggers) && is_callable($handler)))return false;

        // assign new trigger
        $this->triggers[$trigger] = $handler;

        return true;
    }

    public function removeTrigger($trigger){
        // if wrong trigger name provided then quit
        if(!array_key_exists($trigger, $this->triggers))return false;

        // remove trigger
        $this->triggers[$trigger] = null;

        return true;
    }

    // call trigger method:
    // first arg  - trigger name
    // other args - trigger arguments
    protected function trigger(){
        // if no args supplied then quit
        if(!func_num_args())return false;

        // here is supplied args
        $arguments  = func_get_args();

        // extract trigger name
        $trigger    = array_shift($arguments);

        // if trigger handler was assigned then fire it or quit
        return is_callable($this->triggers[$trigger]) ? call_user_func_array($this->triggers[$trigger], $arguments) : false;
    }
}

function check_trigger(){
    print_r(func_get_args());
    print_r(PHP_EOL);
}

function check_add(){
    print_r('"add" trigger'. PHP_EOL);
    call_user_func_array('check_trigger', func_get_args());
}

function check_get(){
    print_r('"get" trigger'. PHP_EOL);
    call_user_func_array('check_trigger', func_get_args());
}

function check_set(){
    print_r('"set" trigger'. PHP_EOL);
    call_user_func_array('check_trigger', func_get_args());
}

function check_exists(){
    print_r('"exists" trigger'. PHP_EOL);
    call_user_func_array('check_trigger', func_get_args());
}

function check_unset(){
    print_r('"unset" trigger'. PHP_EOL);
    call_user_func_array('check_trigger', func_get_args());
}

$victim = new TriggerableArray();

$victim->addTrigger('get', 'check_get');
$victim->addTrigger('set', 'check_set');
$victim->addTrigger('add', 'check_add');
$victim->addTrigger('exists', 'check_exists');
$victim->addTrigger('unset', 'check_unset');

$victim['check'] = 'a';
$victim['check'] = 'b';

$result = $victim['check'];

isset($victim['check']);
unset($victim['check']);

var_dump($result);
?>

显示：

"add" trigger
Array
(
    [0] => check
    [1] => a
)

"set" trigger
Array
(
    [0] => check
    [1] => b
)

"get" trigger
Array
(
    [0] => check
    [1] => b
)

"exists" trigger
Array
(
    [0] => check
)

"unset" trigger
Array
(
    [0] => check
)

string(1) "b"

我假设，您可以使用数组引用参数修改此代码中的构造函数，以便能够传递超全局数组，例如$_COOKIE. 另一种方法是直接在类中替换$this->array为$_COOKIE。另外，还有一种方法可以用匿名函数替换可调用对象。