有人在这个问题中要求提供一个注册变量更改的事件处理程序：PHP如何检测变量的更改？
我试图用PHP的神奇函数__get和__set开发一个快速类。这一直有效，直到我通过引用将成员传递到正常函数中，它不再触发事件。
这是一个错误，还是不可能的事情，或者我只是错过了什么？
<?php
header("content-type: text/plain");
class WatchVar {
private $data = array();
private $org = array();
private $callbacks = array();
public function __set($name, $value) {
if (!array_key_exists($name, $this->data)) {
$this->org[$name] = $value;
} else {
//variable gets changed again!
$this->triggerChangedEvent($name, $value);
}
$this->data[$name] = $value;
}
public function &__get($name) {
if (array_key_exists($name, $this->data)) {
if ($this->data[$name] != $this->org[$name]) {
//variable has changed, return original
//return $this->org[$name];
//or return new state:
return $this->data[$name];
} else {
//variable has not changed
return $this->data[$name];
}
}
}
public function addCallback($name, $lambdaFunc) {
$this->callbacks[$name] = $lambdaFunc;
}
protected function triggerChangedEvent($name, $value) {
//$this->data[$name] has been changed!
//callback call like:
call_user_func($this->callbacks[$name], $value);
}
}
$test = new WatchVar;
$test->addCallback('xxx', function($newValue) { echo "xxx has changed to {$newValue}'n"; });
$test->xxx = "aaa";
echo $test->xxx . "'n";
//output: aaa
$test->xxx = "bbb";
//output: xxx has changed to bbb
echo $test->xxx . "'n";
//output bbb
function messyFunction(&$var) {
$var = "test";
}
messyFunction($test->xxx);
//output: nothing, why?
更改此代码即可工作：
function messyFunction(&$var) {
$var->xxx = "test";
}
messyFunction($test);
//output: xxx has changed to test
//输出：什么都没有，为什么
即使通过引用传递，该函数也只接收成员变量的克隆，而不是实例+魔术函数。