Rewrite Rule for Multilingual Website, Like qTranslate?

I would like to write my own little plugin for language switching. For that, the very first thing would be to get the rewrite rules running. I have been looking around the web for 2 hours, but I couldn’t find an answer to my question yet.

I would like to have it like this: http://www.mysite.com/de/post-title/ or http://www.mysite.com/de/projects/project-title/

So basically, what I’m trying to do is to keep the current url and all it’s parameters, just add the currently active language snippet between the site url and the path. Here is my code so far:

function rewrite_rule_de(){
    add_rewrite_tag('%lang%','([^&]+)');
    add_rewrite_rule('^de/(.+?)/?$', 'index.php?p=$matches[1]&lang=de', 'bottom');
    global $wp_rewrite;
    $wp_rewrite->flush_rules();
}
add_action('init', 'rewrite_rule_de');

Answers:

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Method 1

I got it now , After searched many resources :

function lang_support() {
    return array('en','fr'); // Add your support lang-code (1st place is a default)
}

function rewrite_lang(){
    $langs = lang_support();
    foreach($langs as $lang) {
        add_rewrite_endpoint($lang,EP_PERMALINK|EP_PAGES|EP_ROOT|EP_CATEGORIES);
    }
}
add_action('init','rewrite_lang');

function lang(){
    global $wp_query;
    $langs = lang_support();
    $lang_r = "";
    foreach($langs as $lang) {
        if(isset($wp_query->query_vars[$lang])) {
            $lang_r = $lang;
            $_SESSION['lang'] = $lang_r;
        }
    }
    if(in_array($lang_r,$langs)) {
        return $lang_r;
    } else {
        return $langs[0];
    }
}

function init_session(){session_start();}
add_action('init','init_session',1);

function lang_session() { // Redirect by JS if session is set
    $url_lang= basename($_SERVER['REQUEST_URI']);
    if(!in_array($url_lang,lang_support()) && isset($_SESSION['lang'])) {
        if(!is_404()) {
          wp_redirect(currentURL().$_SESSION['lang'],301);
          exit;
        }
    }
}
add_action('wp_head','lang_session');

function output_buffer() {ob_start();}
add_action('init','output_buffer');

function currentURL() {
    $pageURL=(@$_SERVER["HTTPS"]=="on")?"https://":"http://";
        if($_SERVER["SERVER_PORT"]!="80"){
            $pageURL.=$_SERVER["SERVER_NAME"].":".$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"];
        }else{
            $pageURL.=$_SERVER["SERVER_NAME"].$_SERVER["REQUEST_URI"];
        }
        return $pageURL;
}

Add this code in functions.php. After added code go to wp-admin/options-permalink.php and press Save Changes

So now you can check/use lang code in your template like..

<?php echo lang();?>

or
if( lang() === "en" )

Example work urls with my example code :

http://domain.com/ <-- "en"
http://domain.com/en/ <-- "en"
http://domain.com/fr/ <-- "fr"
http://domain.com/es/ <-- "en" (coz , "es" code not set)

http://domain.com/mypage/ <-- "en" (work with "page")
http://domain.com/mypage/fr/ <-- "fr"
http://domain.com/mypage/es/ <-- "en" (coz , "es" code not set)

http://domain.com/mypost/ <-- "en" (work with "post")
http://domain.com/mypost/fr/ <-- "fr"
http://domain.com/mypost/es/ <-- "en" (coz , "es" code not set)

Better idea / bug fixer / found error + bug ? https://gist.github.com/l2aelba/5244912

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0