<?php
$filename="filename.csv";
header('Content-Type: application/csv; charset=UTF-8');
header("Content-Disposition: attachment; filename=$filename");
echo "\xEF\xBB\xBF";
echo "id,name,tel,addr\n";
echo "001,張三,0933123123,中文地址資料\n";
echo "002,李四,0933222333,中文地址資料\n";
\xEF\xBB\xBF 就是 BOM 字元 (Byte Order Mark)
csv 檔案最前面寫入 BOM 字元，這樣 excel 匯入 csv 檔案時，中文字就不會有亂碼
