$filename = '商品ID_' .  $goods['id']; //文件名称
header("Content-type: application/octet-stream"); //定义浏览器输出类型
header("Accept-Ranges: bytes");
header("Content-Disposition: attachment; filename = {$filename}.txt"); //txt文件名称
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Pragma: public");
echo $content; //输出文件