Fout?

<? 
include "config.php"; 

$lang = $_GET['lang'];

if (isset($lang) == "nl") {
include "lang-nl.php";
echo "De taal is succesvol veranderd in Nederlands.";
setcookie("sqlang", "nl", time()+60*60*24*7*52);
}
elseif (isset($lang) == "eng") {
include "lang-eng.php";
echo "The language is succesfully changed in English.";
setcookie("sqlang", "eng", time()+60*60*24*7*52);
}
else {
echo "The requested language is not supported";
}
?>

<? 
include "config.php"; 
 
$lang = $_GET['lang'];
 
if (isset($lang) == "nl") {
include "lang-nl.php";
echo "De taal is succesvol veranderd in Nederlands.";
setcookie("sqlang", "nl", time()+60*60*24*7*52);
}
elseif (isset($lang) == "eng") {
include "lang-eng.php";
echo "The language is succesfully changed in English.";
setcookie("sqlang", "eng", time()+60*60*24*7*52);
}
else {
echo "The requested language is not supported";
}
?>

setcookie("sqlang","",time());
setcookie("sqlang", "eng", time()+60*60*24*7*52);

setcookie("sqlang","",time());
setcookie("sqlang", "eng", time()+60*60*24*7*52);

<?php
include "config.php"; 

$lang = $_GET['lang'];

if ($lang == "nl") {
include "lang-nl.php";
echo "De taal is succesvol veranderd in Nederlands.";
setcookie("sqlang", "nl", time()+60*60*24*7*52);
}
if ($lang == "eng") {
setcookie("sqlang","",time()+0);
include "lang-eng.php";
echo "The language is succesfully changed in English.";
setcookie("sqlang", "eng", time()+60*60*24*7*52);
}
else {
echo "The requested language is not supported";
}
?>

<?php
include "config.php"; 
 
$lang = $_GET['lang'];
 
if ($lang == "nl") {
include "lang-nl.php";
echo "De taal is succesvol veranderd in Nederlands.";
setcookie("sqlang", "nl", time()+60*60*24*7*52);
}
if ($lang == "eng") {
setcookie("sqlang","",time()+0);
include "lang-eng.php";
echo "The language is succesfully changed in English.";
setcookie("sqlang", "eng", time()+60*60*24*7*52);
}
else {
echo "The requested language is not supported";
}
?>