利用 PHP 8 的注解特性来实现依赖注入

<?php
 
declare(strict_types=1);
 
namespace App\DI;
 
use Attribute;
use ReflectionParameter;
use ReflectionFunction;
use ReflectionException;
use ReflectionAttribute;
use ReflectionNamedArgument;
 
#[Attribute]
class Inject
{
    public function __construct(
        public string $className
    ) {}
}
 
class Container
{
    private array $bindings = [];
 
    public function bind(string $abstract, string $concrete): void
    {
        $this->bindings[$abstract] = $concrete;
    }
 
    public function make(string $abstract): object
    {
        if (isset($this->bindings[$abstract])) {
            $abstract = $this->bindings[$abstract];
        }
 
        return $this->resolve($abstract);
    }
 
    private function resolve(string $concrete): object
    {
        // 尝试创建类的实例
        try {
            $reflectionClass = new ReflectionClass($concrete);
            if (!$reflectionClass->isInstantiable()) {
                throw new ReflectionException("类 {$concrete} 不可实例化");
            }
 
            $constructor = $reflectionClass->getConstructor();
            if (is_null($constructor)) {
                return new $concrete;
            }
 
            $parameters = $constructor->getParameters();
            $dependencies = $this->getDependencies($parameters);
 
            return $reflectionClass->newInstanceArgs($dependencies);
        } catch (ReflectionException $e) {
            // 处理异常
            throw new Exception($e->getMessage());
        }
    }
 
    private function getDependencies(array $parameters): array
    {
        $dependencies = [];
        foreach ($parameters as $parameter) {
            $dependency = $parameter->getType();
            if ($dependency) {
                $dependencyName = $dependency->getName();
                if (class_exists($dependencyName)) {
                    $dependencies[] = $this->make($dependencyName);
                    continue;
                }
            }
 
            $attributes = $parameter->getAttributes(Inject::class, ReflectionAttribute::IS_INSTANCEOF);
            if ($attributes) {
                /** @var ReflectionNamedArgument $argument */
                $argument = $attributes[0]->getArguments()['className'];