Awesome Login!!

<?php
$con=mysqli_connect('host', 'username', 'password', 'db_name');
$key = "supaaaasecretkey!!";



if ($con->connect_errno) {
    echo json_encode('Connect failed: ', $con->connect_error);
}

$rowResult = "";
$un = $_GET['un'];
$pw = $_GET['pw'];
$password = $_GET['password'];
if ($result = $con->query("SELECT password FROM Users WHERE username='{$un}'")) {
  while ($row = $result->fetch_array(MYSQLI_ASSOC)) {
    $row['password'] = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, md5($key), base64_decode($row['password']), MCRYPT_MODE_CBC, md5(md5($key))), "\0");
    $rowResult = $row['password'];
  }
    if (strcmp($pw, $rowResult) !== 0) {
        $result = ["loginSuccess" => "false"];
        echo json_encode($result);
    } else if (strcmp($pw, $rowResult) === 0) {
        $result = ["loginSuccess" => "true"];
        echo json_encode($result);
    }
}
mysqli_close($con);
?>