HTML & PHP Contact form button doesn't work

Question

I am having problem with this contact form I can't get this to work please help? I was working with an HTML contact form, its action is a mail sending php script. But it is not working when i am clicking on the send button. Please someone help me to fix this.

This is contact.php

   <?php

// configure
$from = 'Demo contact form <demo@domain.com>';
$sendTo = 'info@leonardorinaldi.io'; // Add Your Email
$subject = 'New message from contact form';
$fields = array('name' => 'Name', 'subject' => 'Subject', 'email' => 'Email', 'message' => 'Message'); // array variable name => Text to appear in the email
$okMessage = 'Contact form successfully submitted. Thank you, I will get back to you soon!';
$errorMessage = 'There was an error while submitting the form. Please try again later';

// let's do the sending

try
{
    $emailText = "You have new message from contact form\n=============================\n";

    foreach ($_POST as $key => $value) {

        if (isset($fields[$key])) {
            $emailText .= "$fields[$key]: $value\n";
        }
    }

    $headers = array('Content-Type: text/plain; charset="UTF-8";',
        'From: ' . $from,
        'Reply-To: ' . $from,
        'Return-Path: ' . $from,
    );
    
    mail($sendTo, $subject, $emailText, implode("\n", $headers));

    $responseArray = array('type' => 'success', 'message' => $okMessage);
}
catch (\Exception $e)
{
    $responseArray = array('type' => 'danger', 'message' => $errorMessage);
}

if (!empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest') {
    $encoded = json_encode($responseArray);

    header('Content-Type: application/json');

    echo $encoded;
}
else {
    echo $responseArray['message'];
}

This is the html section of the website:

<!--====== Contact ======-->
<section id="contact" class="contact section-padding">
    <div class="contact-overlay"></div>

    <!-- section header -->
    <div class="text-center mb-50">
        <h4 class="tit tit-center">GET IN TOUCH</h4>
    </div>

    <div class="contact-item container">
        <div class="row">

            <!-- contact form -->
            <div class="col-md-8 col-md-offset-2">
                <div class="form" id="contact-form" method="post" action="contact.php">
                    <div class="messages"></div>

                    <div class="controls">

                        <div class="col-sm-6">
                            <div class="form-group">
                                <input id="form_name" type="text" name="name" placeholder="Name *" required="required" data-error="Firstname is required.">
                                <div class="help-block with-errors"></div>
                            </div>
                        </div>

                        <div class="col-sm-6">
                            <div class="form-group">
                                <input id="form_email" type="email" name="email" placeholder="Email *" required="required" data-error="Valid email is required.">
                                <div class="help-block with-errors"></div>
                            </div>
                        </div>

                        <div class="col-sm-12">
                            <div class="form-group">
                                <input id="form_subject" type="text" name="subject" placeholder="Subject">
                                <div class="help-block with-errors"></div>
                            </div>
                        </div>

                        <div class="col-sm-12">
                            <div class="form-group">
                                <textarea id="form_message" name="message" placeholder="Message *" rows="4" required="required" data-error="Message."></textarea>
                                <div class="help-block with-errors"></div>
                            </div>
                        </div>

                        <div class="col-sm-12">
                            <input type="submit" class="button" value="Send Message">
                        </div>
                        <div class="clear-fix"></div>
                    </div>

                </div>
            </div>
        </div>
    </div>
</section>
<!--====== End Contact ======-->

Can someone please help me? there are errors?