从 PHP 中具有动态类名的类中获取静态属性

问题描述

我有这个:

• 一个保存类名的字符串变量 ($classname)
• 一个包含属性名称的字符串变量 ($propertyname)

我想从那个类中获取那个属性，问题是，这个属性是静态的，我不知道该怎么做.

I want to get that property from that class, the problem is, the property is static and I don't know how to do that.

如果属性不是静态的，则应该是:

If the property weren't static, it would have been:

$classname->$propertyname;

如果属性是一个方法，我可以使用 call_user_function

if the property were a method, I could have used call_user_function

call_user_func(array($classname, $propertyname));

但就我而言，我只是迷路了.然而，我希望这是可能的.有了 PHP 拥有的数千个函数，他最好也为此准备一些东西.也许我错过了什么?

But in my case, am I just lost. I am however hoping that it is possible. With the thousands of functions that PHP has, he'd better have something for this as well. Maybe I'm missing something?

谢谢！

• 对于那些有 eval() 解决方案的人:谢谢，但它已经结束了问题的
• 对于那些使用 get _class _vars() 解决方案的人:谢谢，但它似乎返回给定类的默认属性"(php.net)，是的，我希望该值是可变的(即使它确实在某些方面对我有帮助)案例)

• for those with eval() solutions: thanks, but it is out of the question
• for those with get _class _vars() solutions: thanks, but it seems it returns "the default properties of the given class" (php.net), and yes, I would like that value to be changable (even though it does help me in some of the cases)

推荐答案

如果您使用的是 PHP 5.3.0 或更高版本，您可以使用以下内容:

If you are using PHP 5.3.0 or greater, you can use the following:

$classname::$$propertyname;

不幸的是，如果您使用的是低于 5.3.0 的版本，您将无法使用 eval() (get_class_vars() 如果值为动态).

我刚刚说过 get_class_vars() 将不起作用，但显然，可变静态成员是类的默认属性" 的一部分.您可以使用以下包装器:

I've just said get_class_vars() wouldn't work if the value is dynamic, but apparently, variable static members are part of "the default properties of a class". You could use the following wrapper:

function get_user_prop($className, $property) {
  if(!class_exists($className)) return null;
  if(!property_exists($className, $property)) return null;

  $vars = get_class_vars($className);
  return $vars[$property];
}

class Foo { static $bar = 'Fizz'; }

echo get_user_prop('Foo', 'bar'); // echoes Fizz
Foo::$bar = 'Buzz';
echo get_user_prop('Foo', 'bar'); // echoes Buzz

不幸的是，如果你想设置变量的值，你仍然需要使用eval()，但是有了一些验证，它没那么邪恶.

Unfortunately, if you want to set the value of the variable, you will still need to use eval(), but with some validation in place, it's not so evil.

function set_user_prop($className, $property,$value) {
  if(!class_exists($className)) return false;
  if(!property_exists($className, $property)) return false;

  /* Since I cannot trust the value of $value
   * I am putting it in single quotes (I don't
   * want its value to be evaled. Now it will
   * just be parsed as a variable reference).
   */
  eval($className.'::$'.$property.'=$value;');
  return true;
}

class Foo { static $bar = 'Fizz'; }

echo get_user_prop('Foo', 'bar'); // echoes Fizz
set_user_prop('Foo', 'bar', 'Buzz');
echo get_user_prop('Foo', 'bar'); // echoes Buzz

set_user_prop() 使用此验证应该是安全的.如果人们开始将随机的东西放在 $className 和 $property 中，它将退出函数，因为它不是现有的类或属性.从 $value 开始，它实际上从未被解析为代码，因此它们放入的任何内容都不会影响脚本.

set_user_prop() with this validation should be secure. If people start putting random things as $className and $property, it will exit out of the function as it won't be an existing class or property. As of $value, it is never actually parsed as code so whatever they put in there won't affect the script.

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