php - Using class name from a static constant statically in PHP

Question

I have the class name Car stored as a static variable in constants. I would like to use this constant to call the function a. One options is to use an intermediate variable $tmp. I could then call $tmp::a(). Is there a way to do this in one statement? My attempt is below.

class Car{
    public static function a(){
        return 'hi';
    }
}

class Constants{
    public static $use='Car';
}

$tmp=Constants::$use;

echo(${Constants::$use}::a());

IDEOne link

Output is as follows

PHP Notice:  Undefined variable: Car in /home/mU9w5e/prog.php on line 15
PHP Fatal error:  Class name must be a valid object or a string in /home/mU9w5e/prog.php on line 15

Answer 1

总是有call_user_func()：

echo call_user_func( array( Constants::$use, 'a'));

IDEOne 演示

Answer 2

我可以找到@nickb方式的唯一替代方法是使用我从未听说过的东西，但是嘿，这就是 SO 的用途！

我找到了ReflectionMethod，它似乎比 更臃肿call_user_func，但这是我能找到的唯一替代方法：

<?php
class Car{
    public static function a(){
        return 'hi';
    }
}

class Constants{
    public static $use='Car';
}
$reflectionMethod = new ReflectionMethod(Constants::$use, 'a');
echo $reflectionMethod->invoke(new Car());

以上是一个失败的实验，因为Casebash不想创建临时变量。

正如评论中提到的损坏，尽管已经过测试PHP version 5.4.14（我无法做到），但可以使用以下内容：

echo (new ReflectionMethod(Constants::$use, 'a'))->invoke(new Car());

Answer 3

我有疯狂的解决方案，但你永远不应该使用它:^)

echo ${${Constants::$use} = Constants::$use}::a();