php

<?php

        $servername = "mysql.hostinger.co.uk";
        $server_username = "na";
        $server_password = "na";
        $dbName = "u665309766_frdb1";

        $usernameInput = $_POST['usernamePost'];

        $conn = new mysqli($servername, $server_username, $server_password, $dbName);

        if(!$conn)
        {
            die(mysqli_connect_error());
        }

        $sql = "SELECT ID FROM users WHERE username='".usernameInput."' ";
        $result = mysqli_query($conn, $sql);
        $row = mysqli_fetch_assoc($result)

            echo " '".$row['ID']."' ";

?>