Multiple ways of calling parent method in PHP

Question

I wasn't sure why both methods calls in the function Object() { [native code] } worked at first, but I think I now understand. Since the methods are passed down from the parent class and are also present in the extending classes, both should function.

Now I'm wondering whether there is a preferred technique (i.e. best practice) of calling the method (through a parent or this), whether these are actually identical ways of running the same code, or if there are any restrictions when using one over the other.

abstract class Animal {

    function get_species() {

        echo "test";

    }

}

class Dog extends Animal {

    function __construct(){

        $this->get_species();
        parent::get_species();

    }

}

$spike = new Dog;

Can someone please help me with this?