访问父类动态创建的属性

I've searched for this question and surprisingly didn't find anything about it.
I'm creating dynamically created properties into a parent class and I'm trying to access them in a class child.

This is my code:

class Parent_class {
    public $var = '123';

    function __set($name, $value){
        $this->$name = $value;
    }
}

class Child_class extends Parent_class{

}

$parent = new Parent_class();
$child = new Child_class();

$parent->new_property = 'value';

echo $parent->new_property; // returns 'value'
echo $child->var; // returns '123'
echo $child->new_property; // returns 'Notice: Undefined property Child_class::$new_property'

How can I access dynamically created properties in the parent class?

I've managed to get a workaround by using the __get magic method and a static array.

class Parent_class {
    public $var = '123';

    private static $_global = array();

    function __set($name, $value){
        self::$_global[$name] = $value;
    }

    function __get($name){
        return self::$_global[$name];
    }
}

class Child_class extends Parent_class{
    function echoparent(){
        return $this->new_property;
    }
}

$parent = new Parent_class();
$child = new Child_class();

$parent->new_property = 'value';

echo $parent->new_property; // returns 'value'
echo $child->var; // returns '123'
echo $child->new_property; // returns 'value'
echo $child->echoparent(); // returns 'value'