I wrote a code when a user clicks "delete" but it doesn't delete the account, only logs out, I tried searching on internet but nothing was found that helped me. Here's the code:
<?php include('server.php'); 
session_start();
if (isset($_GET['delete'])) {
    $query = "DELETE FROM `users` WHERE `username` = '$username', `password`='$password'";
    mysqli_query($db, $query);
    session_destroy();
    unset($_SESSION['username']);
    unset($_SESSION['password']);
    unset($_SESSION['money']);
    header("location: login.php");
}
?>
Is there any solutions to this code? should I use AND instead of comma, because it didn't work that way, maybe there's an mistake.
$query has the same code that was used on phpmyadmin and it was successful there.
Sorry about the server.php Here is the code of it:
Also using md5 for encrypting passwords is not good idea, I probably need to change it.
Here is login.php where the first code came from (the register button is not programmed properly):
<?php include('server.php'); 
 
 session_start();
 
 if (isset($_GET['delete'])) {
  $stmt = $db->prepare('DELETE FROM users WHERE username = ? AND password = ?');
  $stmt->bind_param('ss', $_SESSION['username'], $_SESSION['password']); // 's' specifies the variable type => 'string'
  $stmt->execute();
  session_destroy();
  unset($_SESSION['username']);
  unset($_SESSION['password']);
  unset($_SESSION['money']);
  header("location: login.php");
 }
?>
<!DOCTYPE html>
<html>
<head>
 <title>Login</title>
 <link rel="stylesheet" type="text/css" href="style.css">
 <script>
  function register() {
   header("location: register.php");
  }
 </script>
</head>
<body>
 </br>
 </br>
 </br>
 </br>
 </br>
 </br>
 </br>
 </br>
 
 <form method="post" action="login.php" align="center">
  <?php include('errors.php'); ?>
  <div class="input-group">
   <label>Username</label>
   <input type="text" name="username" >
  </div>
  <div class="input-group">
   <label>Password</label>
   <input type="password" name="password">
  </div>
  <br/>
  <div class="input-group">
   <button type="submit" class="btn" name="login_user">Login</button>
  </div>
  <p></p></br>
  <p>
   <small class="input-group"> Not yet a member? </small> <button type="button" class="btn2" onclick="register()" name="register">Register</button>
  </p>
 </form>
</body>
</html>This is register.php:
<?php include('server.php') ?>
<!DOCTYPE html>
<html>
<head>
 <title>Registration system PHP and MySQL</title>
 <link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
 </br></br></br></br></br></br></br>
 <div class="header">
  <h2>Register</h2>
 </div>
 
 <form method="post" action="register.php">
  <?php include('errors.php'); ?>
  <div class="input-group">
   <label>Username</label>
   <input type="text" name="username" value="<?php echo $username; ?>">
  </div>
  <div class="input-group">
   <label>Email</label>
   <input type="email" name="email" value="<?php echo $email; ?>">
  </div>
  <div class="input-group">
   <label>Password</label>
   <input type="password" name="password_1">
  </div>
  <div class="input-group">
   <label>Confirm password</label>
   <input type="password" name="password_2">
  </div>
  <div class="input-group">
   <button type="submit" class="btn" name="reg_user">Register</button>
  </div>
  <p>
   Already a member? <a href="login.php">Sign in</a>
  </p>
 </form>
</body>
</html>This is errors.php:
<?php  if (count($errors) > 0) : ?>
 <div class="error">
  <?php foreach ($errors as $error) : ?>
   <p><?php echo $error ?></p>
  <?php endforeach ?>
 </div>
<?php  endif ?>This is index.php:
<?php 
 session_start(); 
 if (!isset($_SESSION['username'])) {
  $_SESSION['msg'] = "You must log in first";
  header('location: login.php');
 }
 if (isset($_GET['logout'])) {
  session_destroy();
  unset($_SESSION['username']);
  unset($_SESSION['password']);
  unset($_SESSION['money']);
  header("location: login.php");
 }
 
?>
<!DOCTYPE html>
<html>
<head>
 <title>Home</title>
 <link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
 <div class="content">
  <!-- notification message -->
  <?php if (isset($_SESSION['success'])) : ?>
   <div class="error success" >
    <h3>
     <?php 
      echo $_SESSION['success']; 
      unset($_SESSION['success']);
     ?>
    </h3>
   </div>
  <?php endif ?>
  <!-- logged in user information -->
  <?php  if (isset($_SESSION['username'])) : ?>
   <p>Welcome <strong><?php echo $_SESSION['username']; ?></strong></p>
   <p> <a href="index.php?logout='1'" style="color: red;">logout</a> </p>
   <p> <a href="login.php?delete='1'" style="color: red;">delete</a> </p>
  <?php endif ?>
 </div>
  
</body>
</html> 
    