//Look for an existing record based on facebookID
$select = $mysqli->prepare("SELECT facebookID, emailAddress FROM user WHERE facebookID = ?");
$select->bind_param('i', $facebookID);
$select->execute();
$select->store_result();

//Logic for how to proceed based on what's found
if ($select->num_rows == 1) {
    //User already exists
    echo "User exists. Set session variables, close window, and refresh origin page.";
} else {
    //User doesn't exist
    echo "User does not exist. Create user.<br><br>";
    if (!$email) {
        //User needs to supply email address
        echo "User has not supplied an email address. Prompt for one before creating account.";
    } else {
        //All info present, proceed with record insertion

        echo "INSERT INTO user VALUES (NULL, '$email', '', '', '$name', '0000-00-00', '', '', 0, 0, 0, now(), '0000-00-00 00:00:00', 0, '$facebookID', '', '', '', '')" . "<br><br>";

        $insert = $mysqli->prepare("INSERT INTO user VALUES (NULL, ?, '', '', ?, '0000-00-00', '', '', 0, 0, 0, now(), '0000-00-00 00:00:00', 0, ?, '', '', '', '')");

        var_dump($insert);

        $insert->bind_param('ssi', $email, $name, $facebookID);
        $insert->execute();