The old PHP 6 is on-hold and even then this behaviour would be "Expected" as we won't know which encoding to use when converting from utf-16.

This is code:
(<?php
include 'functions.php';
if(!$_SESSION['is_logged']==true)
{
    my_header('Регистрация');
if($_POST['form_submit']==1)
{
$login=trim($_POST['login']);
$pas=trim($_POST['pass']);
$pas2=trim($_POST['pass2']);
$email=trim($_POST['mail']);
$name=trim($_POST['name']);

if(strlen($login)<4)
{
$error_array['login']='Кратко име.Трябва да е поне 4 синвола!';
}

if(strlen($pas)<4)
{
$error_array['pass']='Кратка парола!';
}

if($pas!=$pas2)
{
$error_array['pass']='Паролите не въпадат!';
}

if(!eregi("^[[:alnum:]][a-z0-9_.-]*@[a-z0-9.-]+\.[a-z]{2,4}$", $email)) 
{
$error_array['mail']='Невалиден Email адрес!';
}

if (!eregi("^[a-zA-Z0-9_]{3,16}$" ,$name)) 
{
$error_array['name']='Невалидно име!';
}

if(!count($error_array)>0)
{
db_init();
$sql='SELECT COUNT(*) as cnt FROM users WHERE login="'.addcslashes($login).'" OR email="'.addcslashes($email).'"';
$res=mysql_query($sql); 
$row=mysql_fetch_assoc($res);
print ($row);
}

}
else

?>
<form action="register.php" method="POST">
<b>User name</b>:<input type="text" name="login" value="" />
<?php
if($error_array['login'])
{
echo $error_array['login'];
} 
?>
<br />
<b>Парола:</b><input type="password" name="pass" value="" size="30" />
<?php
if($error_array['pass'])
{
echo $error_array['pass'];
} 
?>
<br />
<b>Повтори парола:</b><input type="password" name="pass2" value="" size="30" /><br />
<b>Email:</b><input type="text" name="mail" value="" />
<?php
if($error_array['mail'])
{
echo $error_array['mail'];
} 
?>
<br />
<b>Име:</b><input type="text" name="name" value="" />
<?php
if($error_array['name'])
{
echo $error_array['name'];
} 
?>
<br />
<input type="hidden" name="form_submit" value="1" />
<input type="submit" name="Регистрирай се" value="Регистрирай се" /><br />
</form>
<?php
footer();
}
else 
{
header('Location: index.php');
exit;
})

return error:
(Warning: addcslashes() expects exactly 2 parameters, 1 given in C:\xampp\htdocs\nfs\register.php on line 42

Warning: addcslashes() expects exactly 2 parameters, 1 given in C:\xampp\htdocs\nfs\register.php on line 42
Array)