Contact Form 2018

Good afternoon, guys! I'm super beginner in programming and I'm trying to edit a template, but the contactform part is not working. If anyone can give me a light, I will be very grateful. Below the HTML:

Contact us

                <form id="contactForm" action="sendemail.php" method="POST">
                    <div class="form-group">
                        <label for="InputName">Nome</label>
                        <input type="text" name="name" required="" class="form-control" id="InputName"
                               placeholder="Nome completo">
                    </div>
                    <div class="form-group">
                        <label for="InputEmail">Email</label>
                        <input type="email" name="email" required="" class="form-control" id="InputEmail"
                               placeholder="Email">
                    </div>
                    <div class="form-group">
                        <label for="InputSubject">Assunto</label>
                        <input type="text" name="subject" class="form-control" id="InputSubject"
                               placeholder="Assunto">
                    </div>
                    <div class="form-group">
                        <label for="message-text" class="control-label">Mensagem</label>
                        <textarea class="form-control" rows="4" required="" name="message" id="message-text"
                                  placeholder="Escreva aqui sua mensagem"></textarea>
                    </div>

                    <button type="submit" class="btn btn-primary">Enviar</button>
                </form>

And PHP:

session_cache_limiter( 'nocache' );
header( 'Expires: ' . gmdate( 'r', 0 ) );
header( 'Content-type: application/json' );


$to             = '[email protected]'; //put your email here
$email_template = 'simple.html';  // will find it on email-templates/ directory

$subject    = "SUBJECT";
$email      = strip_tags($_POST['email']);
$name       = strip_tags($_POST['name']);
$message    = nl2br( htmlspecialchars($_POST['message'], ENT_QUOTES) );
$result     = array();


if(empty($name)){

    $result = array( 'response' => 'error', 'empty'=>'name', 'message'=>'<strong>Erro!</strong> Preencha seu nome.' );
    echo json_encode($result );
    die;
} 

if(empty($email)){

    $result = array( 'response' => 'error', 'empty'=>'email', 'message'=>'<strong>Erro!</strong> Preencha seu email.' );
    echo json_encode($result );
    die;
} 

if(empty($message)){

     $result = array( 'response' => 'error', 'empty'=>'message', 'message'=>'<strong>Erro!</strong> Sua mensagem está vazia.' );
     echo json_encode($result );
     die;
}



$headers  = "From: " . $name . ' <' . $email . '>' . "\r\n";
$headers .= "Reply-To: ". $email . "\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-Type: text/html; charset=UTF-8\r\n";


$templateTags =  array(
    '{{subject}}' => $subject,
    '{{email}}'   =>$email,
    '{{message}}' =>$message,
    '{{name}}'    =>$name
    );


$templateContents = file_get_contents( dirname(__FILE__) . '/email-templates/'.$email_template);

$contents =  strtr($templateContents, $templateTags);

if ( mail( $to, $subject, $contents, $headers ) ) {
    $result = array( 'response' => 'success', 'message'=>'<strong>Sucesso!</strong> Email enviado.' );
} else {
    $result = array( 'response' => 'error', 'message'=>'<strong>Erro!</strong> O email não pôde ser enviado.'  );
}

echo json_encode( $result );

die;

Summary, I can not get HTML to pull PHP and submit the form. Only thing that appears is the PHP code itself. If anyone can help me, thank you very much