http авторизация

<?php
  require_once('connectvars.php');
 
  if (!isset($_SERVER['PHP_AUTH_USER']) || !isset($_SERVER['PHP_AUTH_PW'])) {
    // The username/password weren't entered so send the authentication headers
    header('HTTP/1.1 401 Unauthorized');
    header('WWW-Authenticate: Basic realm="Mismatch"');
    exit('<h3>Mismatch</h3>Sorry, you must enter your username and password to log in and access this page. If you ' .
      'aren\'t a registered member, please <a href="signup.php">sign up</a>.');
  }
 
  // Connect to the database
  $dbc = mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);
 
  // Grab the user-entered log-in data
  $user_username = mysqli_real_escape_string($dbc, trim($_SERVER['PHP_AUTH_USER']));
  $user_password = mysqli_real_escape_string($dbc, trim($_SERVER['PHP_AUTH_PW']));
 
  // Look up the username and password in the database
  $query = "SELECT id, username FROM mismatch_user WHERE username = '$user_username' AND password = SHA('$user_password')";
  $data = mysqli_query($dbc, $query);
 
  if (mysqli_num_rows($data) == 1) {
    // The log-in is OK so set the user ID and username variables
    $row = mysqli_fetch_array($data);
    $user_id = $row['id'];
    $username = $row['username'];
  }
  else {
    // The username/password are incorrect so send the authentication headers
    header('HTTP/1.1 401 Unauthorized');
    header('WWW-Authenticate: Basic realm="Mismatch"');
    exit('<h2>Mismatch</h2>Sorry, you must enter a valid username and password to log in and access this page. If you ' .
      'aren\'t a registered member, please <a href="signup.php">sign up</a>.');
  }
 
  // Confirm the successful log-in
  echo('<p class="login">You are logged in as ' . $username . '.</p>');
?>

list($_SERVER['PHP_AUTH_USER'], $_SERVER['PHP_AUTH_PW']) = explode(':', base64_decode(substr($_SERVER['HTTP_AUTHORIZATION'], 6)));

<?php
    if (preg_match('/Basic\s+(.*)$/i', $_SERVER['HTTP_AUTHORIZATION'], $matches))
    {
        list($name, $password) = explode(':', base64_decode($matches[1]));
        $_SERVER['PHP_AUTH_USER'] = strip_tags($name);
        $_SERVER['PHP_AUTH_PW'] = strip_tags($password);
    }
    echo "<p>Username is ", $_SERVER['PHP_AUTH_USER'], "</p>";
    echo "<p>Password is ", $_SERVER['PHP_AUTH_PW'], "</p>";
?>