jak na přihlášení

CREATE TABLE `users` (
  `id` mediumint unsigned NOT NULL auto_increment,
  `username` varchar(20) NOT NULL,
  `password` char(40) NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=MyISAM;

INSERT INTO `users` (`id`, `username`, `password`) VALUES
(NULL, 'admin', SHA1('pokus'));

<?php
include("db.php"); // musi obsahovat funkciu db_connect()
session_start();

// je uzivatel prihlaseny?
if (isset($_SESSION['loged'])) {
  // ano je, zobraz chraneny obsah
  echo "Vitaj " . $_SESSION['username'];
  die();
}

else {
  // uzivatel nie je prihlaseny

  // odoslal uzivatel prihlasovaci formular?
  if (isset($_POST['submit'])) {
    // ano odoslal, over udaje

    $username = trim($_POST['username']);
    if (empty($username))
      die("prazdne policko meno");

    $password = trim($_POST['password']);
    if (empty($password))
      die("prazdne policko heslo");

    db_connect();
    $query = "SELECT * FROM `users` WHERE `username` = '$username'";
    @$result = mysql_query($query);
    if (!$result)
      die("zlyhala komunikacia s DB");

    // je uzivatel zaregistrovany?
    if ($row = mysql_fetch_assoc($result)) {
      // ano uzivatel je registrovany
      $db_passwd = $row['password'];

      // over heslo
      if (sha1($password) == $db_passwd) {
        // heslo O.K.
        $_SESSION['loged'] = "yes";
        $_SESSION['username'] = $username;
        $_SESSION['lastact'] = time();

        header('Location: index.php');
        die();
      }

      else {
        // nespravne heslo
        die("zadali ste nespravne heslo");
      }

    }
    else {
      // uzivatel nie je registrovany, odchpd prec
      die("nie ste registrovany uzivatel, pristup zakazany");
    }

  }

  else {
    // prihlasovaci formular nebol odoslany, zobraz ho

?>
<form action="index.php" method="post">
  meno: <input type="text" name="username" /><br />
  heslo: <input type="password" name="password" /><br />
  <input type="submit" name="submit" value="odoslat" />
</form>
<?php
    die();
  }  

}
?>

$username = trim($_POST['username']);

db.php
<?php
function db_connect()
{
  @$link = mysql_connect('mysql.ic.cz', 'MENO', 'HESLO');
  if (!$link)
    die("zlyhalo pripojenie k DB");

  @$result = mysql_select_db('cw_miniking', $link);
  if (!$result)
    die("zlyhalo pripojenie k DB");

  return true;
}

// je uzivatel prihlaseny?
if (isset($_SESSION['loged'])) {
  // ano je, zobraz chraneny obsah
  echo "Vitaj " . $_SESSION['username'] ."<br>\n";
  echo "<a href=\"logout.php\">odhlasit</a>";
  die();
}

<?php
 session_start();
 if (isset($_SESSION['loged'])) {

   // set cookie expiration time to past. Client delete such cookie
   setcookie(session_name(), "", time() - 259200, '/');

   // delete cookie record from client
   unset($_COOKIE[session_name()]);
	
   // unset all SESSION variables
   $_SESSION = array();

   // and finaly destroy this SESSION
   session_unset();
   session_destroy();

   header('Location: index.php');
   die();
 }

 else {
   die("nepovoleny pristup");
 }

<?
// zde je include souboru s konstantami
mysql_connect("mysql.ic.cz", "cw_miniking", "miniking");
mysql_select_db("users");
mysql_query("INSERT INTO `users` (username,password) VALUES ('$jmeno','$heslo')") or die(mysql_error());
?>

<?
// zde je include souboru s konstantami
mysql_connect("mysql.ic.cz", "cw_miniking", "miniking");
mysql_select_db("cw_miniking");
mysql_query("INSERT INTO `users` (username,password) VALUES ('$jmeno','$heslo')") or die(mysql_error());
?>

mysql_connect($db_host, $db_user, $db_pass);
mysql_select_db($db_name);