indexregi.php

<?php

include "Connection.php";

if($_POST) {
    if (isset($_POST['submit'])) {
        if (!empty($_POST['username']) && !empty($_POST['password'])) {
            $sql = "SELECT * FROM admin WHERE felhasznalonev = '" . $_POST['username'] . "' AND jelszo = '" . $_POST['password'] . "'";
            $result = $connection->query($sql);
            $row = $result->num_rows;
            if ($row == 1) {
                header('Location: fooldal.php');
            } else {
                echo "Hibás felhaszálónév/jelszó!";
            }
        }
    }
}
?>

<html>
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css" integrity="sha384-GJzZqFGwb1QTTN6wy59ffF1BuGJpLSa9DkKMp0DgiMDm4iYMj70gZWKYbI706tWS" crossorigin="anonymous">
    <title>Login</title>
</head>

<body>


<form method="post">
    <label for="username">Felhasználónév:</label>
    <input type="text" name="username"><br>
    <label for="password">Jelszó:</label>
    <input type="password" name="password"><br>
    <input type="submit" name="submit" value="Bejelentkezés">
</form>

<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.6/umd/popper.min.js" integrity="sha384-wHAiFfRlMFy6i5SRaxvfOCifBUQy1xHdJ/yoi7FRNXMRBu5WHdZYu1hA6ZOblgut" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/js/bootstrap.min.js" integrity="sha384-B0UglyR+jN6CkvvICOB2joaf5I4l3gm9GU6Hc1og6Ls7i6U/mkkaduKaBhlAXv9k" crossorigin="anonymous"></script>
</body>

</html>
