如何测试类实例是否属于同一级别的父类之一？

Question

Say I have this:

class Bird{}
class PrettyBird extends Bird{}
class UglyBird extends Bird{}
class Duckling extends UglyBird{}

and I do this:

$bird = new Duckling();

OR

$bird = new UglyBird();

Suppose in my universe all I am interested in is if class belongs to UglyBird or PrettyBird. In case above, I want to test whether $bird belongs to UglyBird (super)class in both cases above.

How?

Currently I can do it by

if (get_class($bird) === UglyBird::class 
    or get_class($bird) === Duckling::class)
    print "MATCH!";

but that's impractical. For example, what if I create a new class that extends UglyBird. I will have to add that class into the if statement.

Answer 1

You can use the function is_subclass_of:

$bird = new Duckling();
$bird2 = new PrettyBird();

var_dump(is_subclass_of($bird, 'UglyBird')); // True
var_dump(is_subclass_of($bird2, 'UglyBird')); // False

Suppose you have a child class of PrettyBird:

class PrettyDuckling extends PrettyBird{}

And you want to know if the child of PrettyBird is a subclass of UglyBird:

$bird3 = new PrettyDuckling();
var_dump(is_subclass_of($bird3, 'PrettyBird')); // True
var_dump(is_subclass_of($bird3, 'UglyBird')); // False

Note that this will work for the parent of the parent as well:

var_dump(is_subclass_of($bird, 'Bird')); // True
var_dump(is_subclass_of($bird2, 'Bird')); // True
var_dump(is_subclass_of($bird3, 'Bird')); // True