URL redirection not working properly: genetates the url http://domain.com/domain.com/ - wordpress

Question

I have a WordPress site in two languages (Hebrew and English) and I need it to redirect according to browser language. I'm using qTranslate plugin to create the content in both languages. This plugin also has a redirection functionality but it creates a redirection only for the homepage and I need the redirection to happen for internal pages as well as the homepage.
Another developer wrote this code for me to create the redirection, but for some reason it creates a funny redirect. It happens only when switching language to Hebrew, then leaving the site and trying to enter directly to http://domain.com/en/ and it redirects you to http://domain.com/domain.com/ (Does not happen when switching to english).
I tried playing with the "header (Location: )" that creates the redirection for Hebrew, but couldn't figure out how to make it work - I tried using the full path instead of relative path, or removing the "/" between $_SERVER['SERVER_NAME'] and $_SERVER['REQUEST_URI'] but got recursive url or url with double "/" (http://domain.com// and also for internal pages http://domain.com//page).
The url structure is:
domain.com/ for Hebrew
domain.com/en/ for English
and when switching language then the parameter $lang=en or $lang=he is being added.
Hope this makes sense, and thanks a lot!
this is the code that is responsible for the redirection:
<?php
if (!isset($_COOKIE["uln"])) :
$lang = substr($_SERVER['HTTP_ACCEPT_LANGUAGE'], 0, 2);
setcookie('uln', $lang, time()+86400*365, '/', '.domain.com'); // cookie stored for a year
$_COOKIE['uln'] = $lang;
endif;
//if lang=(value) is not empty
if(isset($_GET['lang'])) {
$lang = $_GET['lang'];
setcookie('uln', $lang, time()-1, '/', '.domain.com'); //this unsets the cookie for random language selection
//set the cookie "uln" again with the selected language.
setcookie('uln', $lang, time()+86400*365, '/', '.domain.com'); // cookie stored for a year
$_COOKIE['uln'] = $lang;
}
if(($_COOKIE["uln"]) == "en") {
$matched = strncmp("/en/", $_SERVER['REDIRECT_URL'], 3);
if ($matched !== 0) :
header('Location: /en'.$_SERVER['REQUEST_URI']);
endif;
} elseif(($_COOKIE["uln"]) == "he") {
$matched = strncmp("/en/", $_SERVER['REDIRECT_URL'], 3);
if ($matched === 0) :
header('Location: '.$_SERVER['SERVER_NAME'].'/'.$_SERVER['REQUEST_URI']);
endif;
}
?>

Answer 1

instead of
header('Location: '.$_SERVER['SERVER_NAME'].'/'.$_SERVER['REQUEST_URI']);
try
header("Location: http://{$_SERVER['SERVER_NAME']}{$_SERVER['REQUEST_URI']}");
URLs, especially those in Location headers, should include a protocol and domain name. I believe relative URLs in Location headers are a violation of the HTTP RFCs.
By omitting a protocol, you're unintentionally specifying a relative url instead of an absolute one.
Edit: REQUEST_URI is already prefixed with a / so including one in the concat is unnecessary.

Answer 2

You're missing an http:// somewhere, probably in the English -> Hebrew redirect code.
Change
header('Location: '.$_SERVER['SERVER_NAME'].'/'.$_SERVER['REQUEST_URI']);
to
header('Location: http://'.$_SERVER['SERVER_NAME'].'/'.$_SERVER['REQUEST_URI']);