我应该在这个PHP脚本中更改哪些代码来向20多个电子邮件地址发送一封电子邮件？
<?php
$email_to = "youremailaddress@yourdomain.com"; // your email address
$email_subject = "Contact Form Message"; // email subject line
$thankyou = "thankyou.htm"; // thank you page
?>
请举个例子.谢谢.