<form method="POST" action="index.php">
<div class="form-group">
<label for="nom">Nom :</label>
<input type="text" class="form-control" id="nom" name="nom" required>
</div>
<div class="form-group">
<label for="email">Email :</label>
<input type="email" class="form-control" id="email" name="email" required>
</div>

<div class="form-group">
<label for="tel">Tél :</label>
<input type="text" class="form-control" id="tel" name="tel" required>
</div>

<div class="form-group">
<label for="adresse">Adresse :</label>
<input type="text" class="form-control" id="adresse" name="adresse" required>
</div>

<div class="form-group">
<label for="demande">Demande :</label>
<textarea class="form-control" id="demande" name="demande" required></textarea>
</div>

<button type="submit" class="btn btn-default" name="submit">Envoyer</button>
</form>

<?php

$server = "localhost";
$user = "root";
$pass = "";
$dbname = "webmastreverre";

//Creating connection for mysqli

$conn = new mysqli($server, $user, $pass, $dbname);

//Checking connection

if($conn->connect_error){
die("Connection failed:" . $conn->connect_error);
}

if (isset($_POST ['submit'])) {

$nom = $_POST['nom'];
$email = $_POST['email'];
$tel = $_POST['tel'];
$adresse = $_POST['adresse'];
$demande = $_POST['demande'];


$sql = "INSERT INTO doublevi(id,nom,email,tel,adresse,demande) VALUES ('','$nom', '$email', '$tel', '$adresse', '$demande')";

if($conn->query($sql) === TRUE){
echo "<h3> succcess </h3>";
}else{echo "<h3> Failed </h3>";}

}
$conn->close();
?>