Error sending form. This simple code is not working

Question

<form>
<div class="row">
    <div class="col-sm-12 form-group">
        <input class="form-control" id="name" name="name" placeholder="Nome" type="text" required>
    </div>
</div>
<div class="row">
    <div class="col-sm-12 form-group">
        <input class="form-control" id="email" name="email" placeholder="Email" type="email" required>
    </div>
</div>
<div class="row">
    <div class="col-sm-12 form-group">
        <select class="form-control" name="subject" required>
            <option>Assunto</option>
            <option>Orçamento Materiais</option>
            <option>Sugestão</option>
            <option>Trabalhe Conosco</option>
            <option>Outro</option>
        </select>
    </div>
</div>                      
<div class="row">
    <div class="col-sm-12 form-group">
        <textarea class="form-control" id="message" name="message" placeholder="Mensagem" rows="8" required></textarea><br>
    </div>
</div>
<div class="row">
    <div class="col-sm-12 form-group">
        <button type="submit" class="btn btn-primary btn-block btn-lg" name="send" style="border-radius:0px;">ENVIAR</button>
    </div>
</div>
</form>

<?php
//Variáveis enviadas pelo formulário
$nome = $_POST["name"];
$emailUsuario = $_POST["email"];
$assunto = $_POST["subject"];
$sugestao = $_POST["message"];

//Testando
echo $nome;
echo "<br>";
echo $emailUsuario;
echo "<br>";
echo $assunto;
echo "<br>";
echo $sugestao;
echo "<br>";    
?>

Answer 1

The Action attribute is missing with the page that will receive the form or will treat the form of this data and method attribute whether it will be POST or GET

Answer 2

You forgot to put the action and method.

action="page where to go" method="POST"