PHP中的邮件功能标题问题

I am using the following code for mail headers. But it doesn't work properly:

$headers = "From: " . strip_tags($mailfrom) . "
";
$headers .= "Reply-To: ". strip_tags($mailfrom) . "
";
$headers .= "MIME-Version: 1.0
";
$headers .= "Content-Type: text/html; charset=ISO-8859-1
";`

without using the following lines mails are send successfully with html tags:

$headers = "From: " . strip_tags($mailfrom) . "
";
$headers .= "Reply-To: ". strip_tags($mailfrom) . "
";

How to resolve this?

Try like this

$headers = "MIME-Version: 1.0" . "
";
$headers .= "Content-type:text/html;charset=iso-8859-1" . "
";
$headers .='From: '.$mailfrom . "
";
$headers .='Reply-To: '.$mailfrom . "
";