Co vylepšit na skriptu pro přihlášení?

<!--
CONNECT TO THE DB
-->
<?php

include_once("db_pripoj.php");
include_once("db_vytvor.php");
include_once("functions.php");
?>
<!--
CATCHING $GET AND INCLUDING CONTENT
-->
<?php
$action = $_GET["action"];
if ($action == "over_usera") {include ("over_usera.php");}
?>
<form action="index.php?action=over_usera" id="" class="center" name="form" method="post" enctype="multipart/form-data">
  <fieldset>
  <legend>Přihlášení uživatele</legend>
  <label for="prijmeni">Login:</label>
  <br />
  <input type="text" id="log" name="log" />
  <br />
  <label for="heslo">Password:</label>
  <br />
  <input type="password" id="heslo" name="password" />
  <br />
  <br />
  <?php   
//Only if form is submitted
//Pass throught array
if (isset($action))
{
$arr = $hlaska_vlozeni;
foreach ($arr as $value) 
{
echo("$value<br/>");
}
}
unset($value); // break the reference with the last element
?>
  <input name="submitt" type="submit" value="Přihlásit" />

<?php session_start(); ?>
<?php
$prihlasen_admin= "admin.php";
$prihlasen_uzivatel= "uzivatel.php";
$neprihlasen= "index.php";
error_reporting(E_ALL); //Reporting about all errors
$log = (mysql_real_escape_string($_POST["log"]));
$password = (mysql_real_escape_string($_POST["password"]));
if (empty($log) | empty($password))
{
    $hlaska_vlozeni[] = "Nevyplnili jste potřebné údaje";
} 
else
{
//Call function for verifu, that user is admin,normal user or not
overeni($log, $password);
if(($_SESSION['prihlasen'] == 1) & ($_SESSION['is_admin'] == 1))
{
 echo "<script>location.href=\"$prihlasen_admin\";</script>";
}
else if(($_SESSION['prihlasen'] == 1) & ($_SESSION['is_admin'] == 0))
{
 echo "<script>location.href=\"$prihlasen_uzivatel\";</script>";
}
else 
{
 $hlaska_vlozeni[] = "špatně zadané údaje";
}
}
?>

<?php
//FUNKCE PRO OVERENI ZDA JE UZIVATEL ADMIN, CI NENI, PODLE TOHO ZDA MA V TABULCE UVEDENO 0 CI 1
//POKUD SE VSE OSTATNI SHODUJE, T. PRIJMENI A MAIL, TAK PRESMERUJEME BUD NA ADMIN.PHP NEBO NA VYPIS.PHP
function overeni($log, $password)
{
    $_SESSION['prihlasen'] = 0;
    $_SESSION['is_admin'] = 0;
    $q = mysql_query("SELECT je_admin FROM uzivatele WHERE log='$log' AND heslo='$password'");
    if (mysql_num_rows($q) > 0) {
        list($jeadmin) = mysql_fetch_row($q);
        if ($jeadmin) {
            $_SESSION['prihlasen'] = 1;
            $_SESSION['is_admin'] = 1;
			
			
        } else {
            $_SESSION['prihlasen'] = 1;
			$_SESSION['is_admin'] = 0;
        }
    } 
	else {
	
        $_SESSION['prihlasen'] = 0;
		$_SESSION['is_admin'] = 0;
		return false;
    }
}

?>