使用PHP的邮件功能时如何在收件人名称中使用特殊字符

$to = "张三 <<EMAIL>>";
$subject = "邮件主题";
$message = "邮件内容";
$headers = "From: 发件人名称 <<EMAIL>>\r\n";
$headers .= "Content-Type: text/plain; charset=utf-8\r\n";
$headers .= "Content-Transfer-Encoding: 7bit\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "X-Mailer: PHP/" . phpversion();

if (mail($to, '=?UTF-8?B?' . base64_encode($subject) . '?=', $message, $headers)) {
    echo "邮件发送成功";
} else {
    echo "邮件发送失败";
}

$to = array(
    "张三 <<EMAIL>>" => "张三",
    "李四 <<EMAIL>>" => "李四"
);

$subject = "邮件主题";
$message = "亲爱的 {name}，\n\n您好！\n\n这是一封测试邮件。\n\n谢谢！\n";

$headers = "From: 发件人名称 <<EMAIL>>\r\n";
$headers .= "Content-Type: text/plain; charset=utf-8\r\n";
$headers .= "Content-Transfer-Encoding: 7bit\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "X-Mailer: PHP/" . phpversion();

foreach ($to as $email => $name) {
    $message_to_send = str_replace("{name}", $name, $message);
    if (mail($email, $subject, $message_to_send, $headers)) {
        echo "邮件发送给 " . $name . " 成功\n";
    } else {
        echo "邮件发送给 " . $name . " 失败\n";
    }
}