class Animal {} class Dog extends Animal {} $animal = new ReflectionClass('Animal'); $dog = new ReflectionClass('Dog'); var_dump($dog->isSubclassOf($animal)); // true
namespace App\Models; class Animal {} class Dog extends Animal {} $animal = new ReflectionClass('App\Models\Animal'); $dog = new ReflectionClass('App\Models\Dog'); var_dump($dog->isSubclassOf($animal)); // trueThis code checks if the class `Dog` is a subclass of the class `Animal` in the `App\Models` package. Based on the examples, it seems like this function belongs to the core PHP library.