我正在發送一封簡單的電子郵件，需要在正文和主題中使用變量。將變量傳遞到正文中效果很好，但在我的主題行上失敗并顯示未定義的變量$body = "Attached is the " .$name. " Report for ".date('Y-m-d');Mail::raw($body , function ($message) use ($emails,$filepath,$filename) {    $message->from('[email protected]', 'webmail');    $message->attach(storage_path($filepath.'/'.$filename.'.xlsx'));    foreach ($emails['to'] as $email) {        $message->to($email);    }    foreach ($emails['cc'] as $email) {        $message->cc($email);    }    $message->subject("Report for " .$name. " account");});為什么這里用的是body而不是subject呢？