Bu sistemi yapabilecek var mı?

<? require('guvenlik.php');

<?php 

/* Config Section */ 

$pass = '12345'; // Sifreyi buraya giriniz... 
$cookiename = 'sascookie'; // Optional change: Cookie'ye isim veriniz.Basta geçerli olan sascookie dir. 
$expirytime = time()+3600; // Optional change: Sifrenin geçerli oldugu süre "saniye olarak". Basta geçerli olan 1 saatdir. 
$msg = 'Sifre Yanlis.'; // Optional change: parola yanlis mesajidir.basta geçerli olan "Sifre Yanlis"dir. 

/* End Config */ 

/* Logout Stuff - Sept 5, 2005 */ 

if (isset($_REQUEST['logout'])) { 
setcookie($cookiename,'',time() - 3600); // remove cookie/password 
if (substr($_SERVER['REQUEST_URI'],-12)=='?logout=true') { // if there is '?logout=true' in the URL 
$url=str_replace('?logout=true','',$_SERVER['REQUEST_URI']); // remove the string '?logout=true' from the URL 
header('Location: '.$url); // redirect the browser to original URL 
} 
show_login_page(''); 
exit(); 
} 

$logout_button='<form action="'.$_SERVER['REQUEST_URI'].'" method="post"><input type="submit" name="logout" value="Logout" /></form>'; 
$logout_text='<a href="'.$_SERVER['REQUEST_URI'].'?logout=true">Logout</a>'; 

/* End Logout Stuff */ 

/* FUNCTIONS */ 
$encrypt_pass=md5($pass); // encrypt password 

function setmycookie() { 
global $cookiename,$encrypt_pass,$expirytime; 
setcookie($cookiename,$encrypt_pass,$expirytime); 
}  

function show_login_page($msg) { 

?> 

<form action="" method="POST"> 
Şifre:  
<input type="password" name="password" size="20">  
<input type="submit" value="Giriş"> 
<input type="hidden" name="sub" value="sub"> 
</form> 
<?=$msg?> 

<?php } 

/* END FUNCTIONS */ 

$errormsg=''; 
if (substr($_SERVER['REQUEST_URI'],-7)!='sas.php') {// if someone tries to request sas.php 
if (isset($_POST['sub'])) { // if form has been submitted 
$submitted_pass=md5($_POST['password']); // encrypt submitted password 
if ($submitted_pass<>$encrypt_pass) { // if password is incorrect 
$errormsg=$msg; 
show_login_page($errormsg); 
exit(); 
} else { // if password is correct 
setmycookie(); 
} 
} else { 
if (isset($_COOKIE[$cookiename])) { // if cookie isset 
if ($_COOKIE[$cookiename]==$encrypt_pass) { // if cookie is correct 
// do nothing 
} else { // if cookie is incorrect 
show_login_page($errormsg); 
exit(); 
} 
} else { // if cookie is not set 
show_login_page($errormsg); 
exit(); 
} 
} 
} else { 
echo ''; 
} 
?>