In new PHP i can type. Whats better to type?

Use class:

<?php

class Animal {
    protected string $name;
}

class Cat extends Animal {

}

class Dog extends Animal {

}

function doSth(Animal $animal): Animal {
    return $animal;
}

$cat = new Cat();
doSth($cat);

or use interfaces?

<?php

interface Animal {
    public function doSth(): string;
}

class Cat implements Animal {
    public function doSth(): string {
        return "purr";
    }
}

function doSth(Animal $animal): string {
    return $animal->doSth();
}

$cat = new Cat();
doSth($cat);

And how it works it’s fine if iI call to base/parent class in typing or better solution is to use:
function doSth(Cat|Dog $animal): Cat|Dog

I expect to get knowledge what’s better practise