login.php

<?php
include "config.php";
$con = mysqli_connect($MYSQL_HOST, $MYSQL_USER, $MYSQL_PASS, $MYSQL_DB);
$username = $_POST["email"];
$password = $_POST["password"];
$query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
$result = mysqli_query($con, $query);

if (@mysqli_num_rows($result) !== 1) {
  echo "<h1>Login failed.</h1>";
} else {
  echo "<h1>Logged in!</h1>";
  echo "<p>Your flag is: $FLAG</p>";
}

?>