How to fix "This page isn’t working" error on form submit

Question

I'm trying to create a contact form on my Bootstrap 4 website but I get a "This page isn’t working" error page when clicking submit button on the form. I've tried all my best to edit the rd-mailform.php it looks like I won't be able to solve this. I'll appreaciate any help. Thanks.

My modal form code:

<form class="rd-mailform text-left" data-form-output="form-output-global" data-form-type="contact" method="post" action="bat/rd-mailform.php">
                <div class="form-wrap">
                  <label class="form-label" style="color: white;" for="contact-name">NAME<span class="req-symbol">*</span><span class="fa fa-user pull-right"></span> </label>
                  <input class="form-input" id="contact-name" type="text" name="name" data-constraints="@Required">
                </div>
                <div class="form-wrap">
                  <label class="form-label" style="color: white;" for="contact-email">E-MAIL<span class="req-symbol">*</span><span class="fa fa-envelope pull-right"></span></label>
                  <input class="form-input" id="contact-email" type="email" name="email" data-constraints="@Required @Email">
                </div>
                <div class="form-wrap">
                  <label class="form-label" style="color: white;" for="contact-phone">PHONE<span class="req-symbol">*</span><span class="fa fa-mobile pull-right"></span></label>
                  <input class="form-input" id="contact-phone" type="text" name="phone" data-constraints="@Required @PhoneNumber">
                </div>
                <div class="form-wrap">
                  <label class="form-label" style="color: white;" for="contact-email">COMPANY NAME<span class="fa fa-copyright pull-right"></span></label>
                  <input class="form-input" id="contact-company" type="text" name="company" data-constraints="@Required">
                </div>                
                <div class="form-wrap">
                  <label class="form-label" style="color: white;" for="contact-about">ABOUT<span class="fa fa-book pull-right"></span></label>
                  <textarea class="form-input" id="contact-message" name="about" data-constraints="@Required"></textarea>
                </div>
                <div class="form-wrap">
                  <select class="form-input custom-label" id="plan" name="plan" data-constraints="@plan">
                    <option>CHOOSE PLAN</option>
                    <option>Basic</option>
                    <option>Standard</option>
                    <option>Business</option>
                  </select>
                </div>
                <!--Google captcha-->
                <div class="form-wrap text-left form-validation-left">
                  <div class="recaptcha" id="captcha1" data-sitekey="6LfZlSETAAAAAC5VW4R4tQP8Am_to4bM3dddxkEt"></div>
                </div>
                <div class="form-button group-sm text-center text-lg-left">
                  <button class="button button-primary-bright" type="submit">Submit</button>
                </div>
              </form>

rd-mailform.php

<?php

$formConfigFile = file_get_contents("rd-mailform.config.json");
$formConfig = json_decode($formConfigFile, true);

date_default_timezone_set('Lagos/UTC+1');

try {
    require './phpmailer/PHPMailerAutoload.php';

    $recipients = $formConfig['services@tdmstudios.com.ng', 'tdmstudiosofficial@gmail.com'];

    preg_match_all("/([\w-]+(?:\.[\w-]+)*)@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)/" , $recipients, $addresses, PREG_OFFSET_CAPTURE);

    if (!count($addresses[0])) {
        die('MF001');
    }

    function getRemoteIPAddress() {
        if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
            return $_SERVER['HTTP_CLIENT_IP'];

        } else if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
            return $_SERVER['HTTP_X_FORWARDED_FOR'];
        }
        return $_SERVER['REMOTE_ADDR'];
    }

    if (preg_match('/^(127\.|192\.168\.|::1)/', getRemoteIPAddress())) {
        die('MF002');
    }

    $template = file_get_contents('rd-mailform.tpl');

    if (isset($_POST['form-type'])) {
        switch ($_POST['form-type']){
            case 'contact':
                $subject = 'A message from your site visitor';
                break;
            case 'subscribe':
                $subject = 'Subscribe request';
                break;
            case 'order':
                $subject = 'Order request';
                break;
            default:
                $subject = 'A message from your site visitor';
                break;
        }
    }else{
        die('MF004');
    }

    if (isset($_POST['email'])) {
        $template = str_replace(
            array("<!-- #{FromState} -->", "<!-- #{FromEmail} -->"),
            array("Email:", $_POST['email']),
            $template);
    }

    if (isset($_POST['message'])) {
        $template = str_replace(
            array("<!-- #{MessageState} -->", "<!-- #{MessageDescription} -->"),
            array("Message:", $_POST['message']),
            $template);
    }

    // In a regular expression, the character \v is used as "anything", since this character is rare
    preg_match("/(<!-- #\{BeginInfo\} -->)([^\v]*?)(<!-- #\{EndInfo\} -->)/", $template, $matches, PREG_OFFSET_CAPTURE);
    foreach ($_POST as $key => $value) {
        if ($key != "counter" && $key != "email" && $key != "message" && $key != "form-type" && $key != "g-recaptcha-response" && !empty($value)){
            $info = str_replace(
                array("<!-- #{BeginInfo} -->", "<!-- #{InfoState} -->", "<!-- #{InfoDescription} -->"),
                array("", ucfirst($key) . ':', $value),
                $matches[0][0]);

            $template = str_replace("<!-- #{EndInfo} -->", $info, $template);
        }
    }

    $template = str_replace(
        array("<!-- #{Subject} -->", "<!-- #{SiteName} -->"),
        array($subject, $_SERVER['SERVER_NAME']),
        $template);

    $mail = new PHPMailer();


    if ($formConfig['useSmtp']) {
        //Tell PHPMailer to use SMTP
        $mail->isSMTP();

        //Enable SMTP debugging
        // 0 = off (for production use)
        // 1 = client messages
        // 2 = client and server messages
        $mail->SMTPDebug = 0;

        $mail->Debugoutput = 'html';

        // Set the hostname of the mail server
        $mail->Host = $formConfig['mail.tdmstudios.com.ng'];

        // Set the SMTP port number - likely to be 25, 465 or 587
        $mail->Port = $formConfig['465'];

        // Whether to use SMTP authentication
        $mail->SMTPAuth = true;
        $mail->SMTPSecure = "ssl";

        // Username to use for SMTP authentication
        $mail->Username = $formConfig['username'];

        // Password to use for SMTP authentication
        $mail->Password = $formConfig['password'];
    }

    $mail->From = $_POST['services@tdmstudios.com.ng'];

    # Attach file
    if (isset($_FILES['file']) &&
        $_FILES['file']['error'] == UPLOAD_ERR_OK) {
        $mail->AddAttachment($_FILES['file']['tmp_name'],
            $_FILES['file']['name']);
    }

    if (isset($_POST['name'])){
        $mail->FromName = $_POST['name'];
    }else{
        $mail->FromName = "TDM STUDIOS";
    }

    foreach ($addresses[0] as $key => $value) {
        $mail->addAddress($value[0]);
    }

    $mail->CharSet = 'utf-8';
    $mail->Subject = $subject;
    $mail->MsgHTML($template);
    $mail->send();

    die('MF000');
} catch (phpmailerException $e) {
    die('MF254');
} catch (Exception $e) {
    die('MF255');
}