Отправка формы с чекбоксами

HTML

<form id="mail-check">
    <label class="quiz-var two-item">
        <input type="checkbox" class="check1" name="var1[]" value="Аудио-отзывы">
        <span class="title-label">Аудио-отзывы</span>
    </label>
    <label class="quiz-var two-item">
        <input type="checkbox" class="check1" name="var1[]" value="Письменные отзывы">
        <span class="title-label">Письменные отзывы</span>
    </label>
    <label class="quiz-var two-item">
        <input type="checkbox" class="check1" name="var1[]" value="Портфолио">
        <span class="title-label">Портфолио</span>
    </label>
    <label class="quiz-var two-item">
        <input type="checkbox" class="check1" name="var1[]" value="Цены">
        <span class="title-label">Цены</span>
    </label>
    <label class="quiz-var two-item">
        <input type="checkbox" class="check1" name="var1[]" value="Список услуг">
        <span class="title-label">Список услуг</span>
    </label>


    <input type="text" name="phone" placeholder="Ваш телефон*" required>

    <input type="hidden" name="formData" value="Заказали обратный звонок с сайта <?php echo get_home_url(); ?>">
</form>

mail.php

<?php
if(isset($_SERVER['HTTP_X_REQUESTED_WITH']) && !empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest') {
    if (isset($_POST['name'])) {$name = $_POST['name'];}
    if (isset($_POST['phone'])) {$phone = $_POST['phone'];}
    if (isset($_POST['dop'])) {$dop = $_POST['dop'];}
    if (isset($_POST['formData'])) {$formData = $_POST['formData'];}
    
    $chosen = is_array($_POST['var1']) ? $_POST['var1'] : array();
    $chosen = implode (', ', $chosen );
    
 
    $to = "danilsmg@yandex.ru";
    $sendfrom   = "info@kakzhebystro.ru";
    $headers  = "From: " . strip_tags($sendfrom) . "\r\n";
    $headers .= "Reply-To: ". strip_tags($sendfrom) . "\r\n";
    $headers .= "MIME-Version: 1.0\r\n";
    $headers .= "Content-Type: text/html;charset=utf-8 \r\n";
    $subject = "$formData";
    $message = 
    "
            <h3>$formData</h3><br>
            <b>Телефон:</b> $phone<br>
            <b>Выбрали блоки:</b> $chosen<br>
            <b>Другое:</b> $dop<br>
    ";

    $send = mail ($to, $subject, $message, $headers, '-finfo@danilsmg.ru');
    if ($send == 'true')
    {
    echo '';
    }
} else {
    http_response_code(403);
    echo "";
}?>

jQuery

(function(){
    $(document).ready(function () {
         $("#mail-check").submit(function () {
         var formID = $(this).attr('id');
         var formNm = $('#' + formID);
         $.ajax({
         type: "POST",
         url: '/wp-content/themes/shablon/mail.php',
         data: formNm.serialize(),
         success: function (data) {
             $('.modal-smg_boby').fadeOut();
             $('.modal-smg-thanks').fadeIn();
         },
         error: function (jqXHR, text, error) {
             $(formNm).html(error);
         }
         });
         return false;
         });
    });
})();