Contact form problem, html and php

I am using Dreamweaver cc for the following simple contact form which is saved in index.html and I created a mail.php file both saved to -public.html along with styles.css (server is Hostgator.)

The form is simple but looks fine, but the form will not send.

{"code":"MethodNotAllowed","message":"POST is not allowed”}                                                                      see mail.php below:

Can someone please advise me on what I have done incorrect?

index.html

<!-- fourth container contact section -->

        <div class="container-fluid bg-2 text-center" id="Contact">

            <div class = "container">

                <div class = "contact-content flex">

                <div class = "contact-left">

                <div class="title">

                <h3 class="ontop">Contact</h3><br>                        

</div>

        <form action="mail.php" method="post">

        <input type = "text" class = "form-control" placeholder="Your name here ...">

        <input type = "email" class = "form-control" placeholder="Your email here">

<br>

        <input type = "submit" class = "btn-submit btn" value = "Submit">                        

</form>

</div>      

<!-- end of contact section —>

Mail.php file

I have the following code from https://www.php.net/manual/en/function.mail.php, but not sure how to change it to fit my simple form.  I have tried changing it to suit the contact form details:  $to to $text = ‘Your name here’, $subject to $email=‘Your email here’ and $message to $Submit, $headers=‘I used my website.com' and ‘Reply-To: myemail@HostGator.com, but once saved and pressed submit, it opens into a new window with a message {"code":"MethodNotAllowed","message":"POST is not allowed"}

<?php

$to      = 'nobody@example.com';

$subject = 'the subject';

$message = 'hello';

$headers = 'From: webmaster@example.com' . "\r\n" .

    'Reply-To: webmaster@example.com' . "\r\n" .

    'X-Mailer: PHP/' . phpversion();

mail($to, $subject, $message, $headers);

?>

I have contacted HostGator who said that it was not their problem and could not help and that I should contact the web developer, but as I am putting my own website together then that advice was not useful for me.

I hope someone can give me some help on this.

Thank you