动态实例化包含在数组中的PHP类

I'm trying to instantiate some classes in an array. This is the scenario: I have many classes, e.g.:

class Class0 extends NumberedClasses{...}
class Class1 extends NumberedClasses{...}
class Class2 extends NumberedClasses{...}

They will increase over the time, so instead of instantiating them this way:

$instances0 = new Class0();
$instances1 = new Class1();
$instances2 = new Class2();

I want to have a getter method, like this one:

function getStrategies(){
   return array(Class0, Class1, Class2);
}

So I can just add classses in that array in the future, and call it this way:

$strategies = $this->getStrategies();
for ($strategies as $strategy) { 
    $instance = new $strategy();
}

I'm used to do something similar with js, where I have the window object, so I can instantiate classes even just with a string (new window["Class1"]). But I'm new with PHP and can't find the way to do that.

Thanks in advance,

It may be suggested that using an Intermediary Class to manage these instances will be much ideal. Consider this:

    <?php

        class NumberedClasses{}
        class Class0 extends NumberedClasses{}
        class Class1 extends NumberedClasses{}
        class Class2 extends NumberedClasses{}


        class InstanceHelper {

            /**
             * @var array
             */
            protected $instances = array();

            public function addInstance($instanceKey, $instance) {
                if(!array_key_exists($instanceKey, $this->instances)){
                    $this->instances[$instanceKey] = $instance ;
                }
            }

            public function addInstances(array $arrayOfInstances) {
                foreach($arrayOfInstances as $instanceKey=>$instance){
                    if(!array_key_exists($instanceKey, $this->instances)){
                        $this->instances[$instanceKey] = $instance ;
                    }
                }
            }

            public function removeInstance($instanceKey) {
                if(array_key_exists($instanceKey, $this->instances)){
                    unset($this->instances[$instanceKey]);
                }
                return $this->instances;
            }

            public function getAllInstances() {
                return $this->instances;
            }
        }

Now; with the Class InstanceHelper, You can easily manage your instances... even add Instances, remove Instance and so on.... Again consider this tests:

    <?php

        $insHelper          = new InstanceHelper();
        $instances          = array(
            'c0'    =>  new Class0(),
            'c1'    =>  new Class1(),
            'c2'    =>  new Class2(),
        );

        $insHelper->addInstances($instances);

        var_dump($insHelper->getAllInstances());
        var_dump($insHelper->removeInstance('c1'));

Here are the results of both var_dumps:

        ::VAR_DUMP 1::
        array (size=3)
          'c0' => 
            object(Class0)[2]
          'c1' => 
            object(Class1)[3]
          'c2' => 
            object(Class2)[4]



        ::VAR_DUMP 2::
        array (size=2)
          'c0' => 
            object(Class0)[2]
          'c2' => 
            object(Class2)[4]