Code tags do not properly work

If you add ( in text editor – text mode) code as the below following, nicely wrapped into opening and closing code tags, the inserted code gets messed up.

This is a problem, if you want to build a code library.

Can anybody mention a workaround or solution to this problem?

Test with this Code:

add_filter('wp_nav_menu_items', 'wpml_secondary_lang_nav_menu_item', 10, 2);
function wpml_secondary_lang_nav_menu_item($items, $args) {
// uncomment this to find your theme's menu location
//echo "args: <pre>"; print_r($args); echo "</pre>";

	// adjust $args->theme_location == 'primary' in the conditional below to specify the menu location
	if(function_exists('icl_get_languages') && $args->theme_location == 'primary'){
		global $sitepress_settings, $sitepress;

		$languages = $sitepress->get_ls_languages();
		if(!empty($languages)){
			// collect secondary languages in array
			$secondary_languages = array();
			foreach($languages as $code => $lang){
				if(!$lang['active']){
					$secondary_languages[] = $lang;
				}
			}
			if(!empty($secondary_languages)){
				$items .= '<li class="menu-item menu-item-language">';
					if(isset($args->before)){
						$items .= $args->before;
					}
					$items .= '<a href="' . $secondary_languages[0]['url'] . '">';
					if(isset($args->link_before)){
						$items .= $args->link_before;
					}
					// from this point on, uncomment whatever output you like
					// flag-only
					/*$items .= '<img class="iclflag" src="' . $secondary_languages[0]['country_flag_url'] . '" width="18" height="12" alt="' . $secondary_languages[0]['translated_name'] . '" />';*/

					// translated name - only
					/*$items .= $secondary_languages[0]['translated_name'];*/
					if(isset($args->link_after)){
						$items .= $args->link_after;
					}
					$items .= '</a>';
					if(isset($args->after)){
						$items .= $args->after;
					}
				$items .= '</li>';
			}
		}
	}
return $items;
}

Actually I am quiet surprised it does not get cut off in this very post!