validation.php

<?php
    $servername = "localhost";
    $username = "root";
    $password = "";
    $dbname = "gymtastic";
    // Create connection
        $conn = new mysqli($servername, $username, $password, $dbname);
    // Check connection
    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }else{
        echo "Connected <br>";
    }
    if (isset($_POST['value']))
    {
          echo "value bestaat <br>";
    }else{
        echo "value bestaat niet <br>";
    }
    if (isset($_POST['name']))
    {
          echo "name bestaat <br>";
    }else{
        echo "name bestaat niet <br>";
    }
    if (isset($_POST['selection']))
    {
          echo "selection bestaat <br>";
    }else{
        echo "selection bestaat niet <br>";
    }
    if (isset($_POST['heat']))
    {
          echo "heat bestaat <br>";
    }else{
        echo "heat bestaat niet <br>";
    }

    if (isset($_POST[''])) {
        $name = $_POST['name'];
        $selection = $_POST['selection'];
        $value = $_POST['value'];
        $heat = $_POST['heat'];
        $sql = "INSERT INTO elements (name, selection, value, heat)VALUES('$name','$selection','$value','heat')";

        if (!mysqli_query($conn, $sql)){
            die('Error: ' . mysqli_error($conn));
        }
    }

?>

<!DOCTYPE html>
<html>
<head>
    <title>Gymtastic</title>
    <link rel="stylesheet" type="text/css" href="style/style.css">
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- Latest compiled and minified CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">

    <!-- jQuery library -->
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>

    <!-- Latest compiled JavaScript -->
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
    <div class="container">
        <div class="row">
            <div class="col-md-12">
                <div class="title">
                    <h1>Gymtastic</h1>
                </div>
            </div>
        </div>
    </div>
</body>
</html>