<form id="form" name="contactForm" method="post" action="php/formulario_contactos.php">
            <div>
                <label for="name">Your name</label>
                <input type="text" id="name" name="name" maxlength="40" placeholder="Write your Name">
                <span class="error"><?php echo $nameError; ?></span>
            </div>
            <div>
                <label for="email">Your email</label>
                <input type="email" id="email" name="user_mail" placeholder="email@example.com">
                <span class="error"><?php echo $emailError; ?></span>
            </div>
            <div>
                <label for="topic">Select Topic</label>
                <select id="topic" name="topic">
                    <option selected disabled hidden value="">Choose a Topic</option>
                    <option value="link">Site Link</option>
                    <option value="copyright">Copyright</option>
                    <option value="errors">Site/Article errors</option>
                    <option value="feedback">Feedback</option>
                    <option value="other">Other</option>
                </select>
                <span class="error"><?php echo $topicError; ?></span>
            </div>
            <div>
                <label for="msg">Your message</label>
                <textarea id="msg" name="user_message" placeholder="Write your message"></textarea>
                <span class="error"><?php echo $mensagemError; ?></span>
            </div>
            <div class="button">
                <button type="submit" id="submit">Submit</button>
                <span class="success"><?php echo $successMessage; ?></span>
            </div>
        </form>

<?php

$servername = "localhost:3306";
$username = "root";
$password = "";
$dbname = "site_comboios";

//Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed:" . $conn->connect_error);
}

$name = mysqli_real_escape_string($conn,$_POST['name']);
$email = mysqli_real_escape_string($conn,$_POST['user_mail']);
$topic = mysqli_real_escape_string($conn,$_POST['topic']);
$mensagem = mysqli_real_escape_string($conn,$_POST['user_message']);


$nameError = "";
$emailError = "";
$topicError = "";
$mensagemError = "";
$successMessage = "";

if( isset($_POST["submit"])) {
if(empty($_POST['name'])) {
    $nameError = "Name is required";
} else {
    $name = test_input($_POST['name']);
    if(!preg_match("/^[a-zA-Z ]*$/", $name)) {
        $name = "Only letters and white space allowed";
    }
}

if(empty($_POST['user_mail'])) {
    $emailError = "Email is required";
} else {
    $email = test_input($_POST['user_mail']);
}

if(empty($_POST['topic'])) {
    $topicError = "Choose a category";
} else {
    $topic = test_input($_POST['topic']);
}

if(empty($_POST['user_message'])) {
    $mensagemError = "Please, write your feedback";
} else {
    $mensagem = test_input($_POST['user_message']);
}
}

function test_input($data)
{
$data = trim($data);
$data =stripslashes($data);
$data =htmlspecialchars($data);
return $data;
}

$sql = "INSERT INTO formulario_contactos (Nome, Email, Topico, Mensagem)
VALUES ('$name', '$email' , '$topic' , '$mensagem')";

if ($conn->query($sql) === TRUE) {
echo 'Your message has been successfully sent';
} else {
echo 'Error'. $sql . $conn->error;
}

$conn->close();