introduction-php-reflection-reflection-class-get-constructor.php

<?php

class UserRepository
{ }

class UserController {
    private $userRepository;

    public function __construct(UserRepository $repository)
    {
        $this->userRepository = $repository;
    }
}

$userReflected = new ReflectionClass(UserController::class);
var_dump($userReflected);
// object(ReflectionClass)#1 (1) {
//  ["name"]=>
//  string(14) "UserController"
//}

$constructorParameters = $userReflected->getConstructor()->getParameters();

$argumentsToConstruct = [];

foreach ($constructorParameters as $parameter) {
    $name = $parameter->getClass()->name;
    var_dump($name);
    // string(14) "UserRepository"

    $instance = new $name();
    var_dump($instance);
    // object(UserRepository)#2 (0) {
    //}

    $argumentsToConstruct[] = $instance;
}

$userController = new UserController(...$argumentsToConstruct);
var_dump($userController);
// object(UserController)#4 (1) {
//  ["userRepository":"UserController":private]=>
//  object(UserRepository)#2 (0) {
//  }
//}