php利用反射优雅的实现工厂

function factory($class, $args){
  if(class_exists($class)){
    return (new \ReflectionClass($class))->newInstanceArgs($args);
  }
}

$db = array(
  'PDO',
  array(
   'mysql:dbname=test;host=localhost',
   'root',
   'root',
   array(PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC)
  )
);

var_dump(factory($db[0], $db[1])->query('show tables')->fetchAll());