直接用代码来说明

namespace Database;
use ReflectionMethod;

class connection
{
    public function __construct (){

    }
    //通过构造方法进行依赖注入MySQL_Adapter
    public function connect (MySQL_Adapter $MySQL_Adapter)
    {
        echo "connection:";
        echo "\n";
        $MySQL_Adapter->connect();
    }
}

class MySQL_Adapter
{

    public function __construct ($instance_parameters){
    	echo 'MySQL_Adapter instance,parameters:'.$instance_parameters;
    	echo "\n";
    }
    public function connect (){
        echo "MySQL_Adapter connect";
        echo "\n";
    }
}

class app
{

    public static function run ($instance, $method)
    {
        // 利用发射机制获取实例$instance方法method的内部信息
        $reflector = new ReflectionMethod($instance, $method);
 
        $parameters = array();
        // 遍历方法$method的参数
        foreach ($reflector->getParameters() as $key => $parameter)
        {
            
            $class = $parameter->getClass();
            //如果参数是类的话
            if ($class)
            {
                //获取类名
            	$reflector_classname = $class->name;
                //进行实例化
                $classname_instance = new $reflector_classname('reflector');
                //保存实例
                $parameters[$key] = $classname_instance;
            }
        }
        //执行$instance实例的方法$method，并且把参数$parameters传给方法
        //$parameters包括已经被实例化的对象参数MySQL_Adapter
        call_user_func_array([$instance,$method],$parameters);
    }
}

$connection = new connection();
app::run($connection, 'connect');