可以在类方法中使用类名属性实例化PHP实例（在一行代码中）？

Question

I would like to be able to instantiate a class using a class name stored in another class's property, and I want to do this with one line of code, as in the comments in the code below (and it should work on at least one recent version of PHP 5). Is this possible?

<?php

class Foo {

  public function doFoo() {

    echo "foo
";

  }

}

class Bar {

  function __construct($className) {

    $this->className = $className;

  }

  public function doBar() {

    //INSTEAD OF THESE TWO LINES...
    //$className = $this->className;
    //$instance = new $className();

    //I WOULD LIKE THIS (OR SOME OTHER) ONE-LINER TO WORK:
    $instance = $this->className();

    $instance->doFoo();

  }

}

$bar = new Bar('Foo');
$bar->doBar();

EXPECTED OUTPUT:

foo

Answer 1

There is an obvious typo in the code which is calling a function instead of a constructor, and can be fixed as follows:

$instance = new $this->className();

That does the trick.