public static function __callStatic($method, $parameters)
{
  $instance = new static; //这里的$instance就是User类的实例对象

  return call_user_func_array([$instance, $method], $parameters);
}

public function __call($method, $parameters)
{
  if (in_array($method, ['increment', 'decrement'])) {
    return call_user_func_array([$this, $method], $parameters);
  }

  $query = $this->newQuery(); //返回Illuminate\Database\Eloquent\Builder对象

  return call_user_func_array([$query, $method], $parameters);
}

/**
 * Run the query as a "select" statement against the connection.
 *
 * @return array
 */
protected function runSelect()
{
  return $this->connection->select($this->toSql(), $this->getBindings(), ! $this->useWritePdo); //调用connection 对象的select方法
}

/**
 * Get a new query builder for the model's table.
 *
 * @return \Illuminate\Database\Eloquent\Builder
 */
public function newQuery()
{
  $builder = $this->newQueryWithoutScopes();

  return $this->applyGlobalScopes($builder);
}

/**
 * Get a new query builder that doesn't have any global scopes.
 *
 * @return \Illuminate\Database\Eloquent\Builder|static
 */
public function newQueryWithoutScopes()
{
  $builder = $this->newEloquentBuilder(
    $this->newBaseQueryBuilder() //这个方法返回
  );

  // Once we have the query builders, we will set the model instances so the
  // builder can easily access any information it may need from the model
  // while it is constructing and executing various queries against it.
  return $builder->setModel($this)->with($this->with);
}

/**
 * Get a new query builder instance for the connection.
 *
 * @return \Illuminate\Database\Query\Builder
 */
protected function newBaseQueryBuilder()
{
  $conn = $this->getConnection(); \\连接数据库并返回connection对象

  $grammar = $conn->getQueryGrammar();

  return new QueryBuilder($conn, $grammar, $conn->getPostProcessor()); //Illuminate\Database\Query\Builder

}

/**
 * Create a single database connection instance.
 *
 * @param array $config
 * @return \Illuminate\Database\Connection
 */
protected function createSingleConnection(array $config)
{
  //创建连接器对象并连接数据库返回pdo对象
  $pdo = $this->createConnector($config)->connect($config);
  //传入PDO对象、并返回connection对象，connection对象负责查询数据库
  return $this->createConnection($config['driver'], $pdo, $config['database'], $config['prefix'], $config); 

}