폼메일 수신자 제목 이상

<?php
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

require __DIR__ . '/lib/PHPMailer/src/PHPMailer.php';
require __DIR__ . '/lib/PHPMailer/src/Exception.php';
require __DIR__ . '/lib/PHPMailer/src/SMTP.php';

use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

include_once('./_common.php');
include_once(G5_CAPTCHA_PATH.'/captcha.lib.php');

if (!chk_captcha()) {
    alert('자동등록방지 숫자가 틀렸습니다.');
}

if (isset($_POST['email'])) {

    $email_to = "eseragh@gmail.com"; // 수신메일
    $email_subject = "[나무 속 자연공작소] {$_POST['first_name']} 님의 문의사항. {$_POST['mainlTitle']}";
    $email_subject = '=?UTF-8?B?' . base64_encode($email_subject) . '?=';

    if (!isset($_POST['first_name']) ||
        !isset($_POST['phone']) ||
        !isset($_POST['email']) ||
        !isset($_POST['mainlTitle']) ||
        !isset($_POST['comments']) ||
        !isset($_POST['agree'])) {
        die('Sorry.\nThere is a problem with the form you submitted.\nPlease check the form again.');
    }

    $first_name = $_POST['first_name']; // required
    $phone = $_POST['phone']; // not required
    $email = $_POST['email']; // required
    $comments = $_POST['comments']; // required
    $mainlTitle = $_POST['mainlTitle']; // required
    $group = isset($_POST['group']) ? implode(', ', $_POST['group']) : ''; // 다중체크
    $agree = $_POST['agree']; // required

    function clean_string($string) {
        $bad = array("content-type", "bcc:", "to:", "cc:", "href");
        return str_replace($bad, "", $string);
    }

    $email_message = "성명 : " . clean_string($first_name) . "<br><br>";
    $email_message .= "연락처 : " . clean_string($phone) . "<br><br>";
    $email_message .= "E-mail : " . clean_string($email) . "<br><br>";
    $email_message .= "제목 : " . clean_string($mainlTitle) . "<br><br>";
    $email_message .= "분야 : " . clean_string($group) . "<br><br>"; // 다중체크
    $email_message .= "문의 내용 : " . clean_string($comments) . "<br><br>";
    $email_message .= "개인정보처리방침 : " . clean_string($agree) . "<br><br>";

    // PHPMailer setup
    $mail = new PHPMailer(true);
    try {
        // Server settings
        $mail->isSMTP();
        $mail->Host = 'smtp.gmail.com';
        $mail->SMTPAuth = true;
        $mail->Username = 'eseragh@gmail.com'; // Your Gmail address
        $mail->Password = 'orqscwfrxfrxoenf'; // Your Gmail password or App Password
        $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
        $mail->Port = 587;

        // Recipients
        $mail->setFrom('eseragh@gmail.com', '한국세라프');
        $mail->addAddress($email_to);

        // Content
        $mail->isHTML(true);
        $mail->Subject = $email_subject;
        $mail->Body = $email_message;

        $mail->send();
        // Use header for redirect after PHP execution
        header("Location: /home/sub04_04.php");
        exit();
    } catch (Exception $e) {
        echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
    }
}
?>