Instantiating one instance each of parent's class children? - php

Question

For testing my stuff i would like to automaticaly instantiate one instance each per child of a parent class i name, without calling the class name manually (its too many).
For example:
Class Animal {
public weight;
}
Class Dog extends Animal {
public weight = 20;
}
Class SmallDog extends Dog {
public weight = 18;
}
Class Cat extends Animal {
public weight = 10;
}
function xy(){
$classes = array();
foreach parent->child as child(){
$classes[] = new child()
}
//$classes = [Dog, SmallDog, Cat]
}
Is something like (tm) doable and if so, how ?
As further information, i have an autoload_register that holds each class, but it also holds various classes i dont want to instantiate.
Also, relative to the above example, i have Animal, Dog and Cat all assembled in a single file, lets call it animal.php.
In the code above, i would except to get an instance of anything below Animal, including SmallDog. If its not possible that way, i would be okay with getting Dog and Cat and calling the function with parent being Dog (to get SmallDog instantiated).
thanks for your advice,

Answer 1

This is not really useful in real case scenarios but using #axiac comment you can implement ChildrenResolver class:
class ChildrenResolver
{
protected $defaultClasses = [
0 => 'stdClass',
1 => 'Exception',
2 => 'ErrorException',
// ...
];
protected $declaredClasses;
public function __construct(array $declaredClasses = null)
{
if (is_null($declaredClasses)) {
$declaredClasses = array_diff(
get_declared_classes(),
$this->defaultClasses
);
}
$this->declaredClasses = $declaredClasses;
}
public function getChildClasses($class)
{
return array_filter(
$this->declaredClasses,
function ($declaredClassName) use ($class) {
$declaredClass = new ReflectionClass($declaredClassName);
while(($parent = $declaredClass->getParentClass())) {
if ($parent->name === $class) {
return true;
}
$declaredClass = $parent;
}
return false;
}
);
}
public function getDirectChildClasses($class)
{
return array_filter(
$this->declaredClasses,
function ($declaredClassName) use ($class) {
$declaredClass = new ReflectionClass($declaredClassName);
$parent = $declaredClass->getParentClass();
return $parent ? $parent->name === $class : false;
}
);
}
}
The idea is pretty simple. We loop over declared classes (obtained via get_declared_classes), reflect every class using ReflectionClass and compare parent, which we get from ReflectionClass::getParentClass, with given parent. For the sake of convinience I used array_filter function.
Having this class you can resolve children like this:
$childrenResolver = new ChildrenResolver;
var_dump($childrenResolver->getChildClasses('Animal'));
var_dump($childrenResolver->getDirectChildClasses('Animal'));
var_dump($childrenResolver->getChildClasses('Dog'));
Here is working demo.