https://blog.toright.com/posts/1471/php-%e8%99%95%e7%90%86%e6%83%b1%e4%ba%ba%e7%9a%84-bom-%e5%95%8f%e9%a1%8c%ef%bc%8c%e8%bc%b8%e5%87%ba-excel-%e6%a0%bc%e5%bc%8f%e5%8a%a0%e5%85%a5-bom