Code

<?php
echo "Starting registeruser.php<br>";
$servername = "localhost";
$username = "u437128601_admin";
$password = "sqladmin2016";
$dbname = "u437128601_all";

// Create Connection

$conn = new mysqli($servername, $username, $password, $dbname);

// Check Connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully<br>";

    // Validate, Sanitize and Execute

    /*if ($username == "" || $username == !isset($username)) {
        die("Empty string!");
    } else {
        $username = filter_var($username, FILTER_SANITIZE_STRING);
    }
    */

    // Prepare and Bind

    if ($stmt = $conn->prepare("INSERT INTO WebsiteUsers (username, password, email, growid, world, gender) VALUES (?, ?, ?, ?, ?, ?)")) {
        $stmt->bind_param("ssssss", $username, $password, $email, $growid, $world, $gender);
    } else {
        echo "Prepare() returned false! VAR_DUMP RESULTS: ";
        var_dump(error);
    }

    // Set Parameters & Filter

    $username = filter_input(INPUT_POST, 'u_username', FILTER_UNSAFE_RAW, FILTER_FLAG_STRIP_LOW);
    echo $username;
    $password = $_POST['u_pwd'];
    $email = $_POST['u_email'];
    $growid =  $_POST['u_growid'];
    $world = $_POST['u_world'];
    $gender = $_POST['u_gender'];

    $password = filter_var($password, FILTER_SANITIZE_STRING);
    $email = filter_var($email, FILTER_SANITIZE_EMAIL);
    $growid = filter_var($growid, FILTER_SANITIZE_STRING);
    $world = filter_var($world, FILTER_SANITIZE_STRING);
    $gender = filter_var($gender, FILTER_SANITIZE_STRING);

    $stmt->execute();

    /* NON-PREPARED STATEMENT
    $query = "INSERT INTO WebsiteUsers (username, password, email, growid, world, gender) VALUES ('$username', '$password', '$email', '$growid', '$world', '$gender')";
    $data = mysql_query ($query)or die(mysqli_error());
    if ($data) {
       echo "Registration completed.";
    }
    */
?>