i18n: Update set_ui_language()

Set phpIPAM UI locale in order of preference
  1) $_SESSION['ipamlanguage']
  2) Administration -> phpIPAM settings -> Default language
  3) LC_ALL environment
  4) HTTP_ACCEPT_LANGUAGE header

Set LANGUAGE environment for Ubuntu.

app/login/index.php

@@ -115,15 +115,10 @@ if(@$config['requests_public']===false) {
 	<?php
 	# set default language
 	if(isset($User->settings->defaultLang) && !is_null($User->settings->defaultLang) ) {
-		# get language
+		# get global default language
 		$lang = $User->get_default_lang();
-
-		if (is_object($lang)) {
-			putenv("LC_ALL=".$lang->l_code);
-			setlocale(LC_ALL, $lang->l_code);					// set language
-		}
-		bindtextdomain("phpipam", "./functions/locale");	// Specify location of translation tables
-		textdomain("phpipam");								// Choose domain
+		if (is_object($lang))
+			set_ui_language($lang->l_code);
 	}
 	?>
 

functions/classes/class.User.php

@@ -303,7 +303,7 @@ class User extends Common_functions {
                     $this->reset_inactivity_time();
                     $this->update_activity_time ();
                     # bind language
-                    $this->set_ui_language();
+                    set_ui_language();
                 }
             }
         }
@@ -460,21 +460,6 @@ class User extends Common_functions {
         setcookie("phpipamredirect", preg_replace('/^\/+/', '/', $_SERVER['REQUEST_URI']), time()+10, "/", null, null, true);
     }
 
-    /**
-     * Sets translation for logged in user
-     *
-     * @access private
-     * @return void
-     */
-    private function set_ui_language () {
-        if(strlen($_SESSION['ipamlanguage'])>0)     {
-            putenv("LC_ALL=$_SESSION[ipamlanguage]");
-            bindtextdomain("phpipam", dirname(__FILE__)."/../locale");    // Specify location of translation tables
-            setlocale(LC_ALL, $_SESSION['ipamlanguage']);        // set language
-            textdomain("phpipam");                                // Choose domain
-        }
-    }
-
     /**
      * Checks if system is in maintaneance mode and exits if it is
      *

functions/functions.php

@@ -28,6 +28,9 @@ if (Config::ValueOf('proxy_enabled') == true) {
 /* global and missing functions */
 require('global_functions.php');
 
+/* Set UI language */
+set_ui_language();
+
 /* @http only cookies ------------------- */
 if(php_sapi_name()!="cli")
 	ini_set('session.cookie_httponly', 1);

functions/global_functions.php

@@ -138,3 +138,48 @@ function php_feature_missing($required_extensions = null, $required_functions =
 
 	return false;
 }
+
+/**
+ * Set phpIPAM UI locale in order of preference
+ *  1) $_SESSION['ipamlanguage']
+ *  2) Administration -> phpIPAM settings -> Default language
+ *  3) LC_ALL environment
+ *  4) HTTP_ACCEPT_LANGUAGE header
+ */
+function set_ui_language($default_lang = null) {
+
+	if (php_feature_missing(["gettext", "pcre"]))
+		return;
+
+	$application_langs = [$_SESSION['ipamlanguage'], $default_lang, getenv("LC_ALL")];
+
+	$http_accept_langs = preg_replace("/;.*$/", "", explode(',', $_SERVER['HTTP_ACCEPT_LANGUAGE']));
+
+	// Try each langage in order of preference
+	$langs = array_merge($application_langs, $http_accept_langs);
+
+	foreach($langs as $lang) {
+		if (!is_string($lang) || strlen($lang)==0)
+			continue;
+
+		if (!file_exists(dirname(__FILE__)."/locale/$lang/LC_MESSAGES/phpipam.mo"))
+			continue;
+
+		putenv("LC_ALL=".$lang);
+
+		// https://help.ubuntu.com/community/EnvironmentVariables
+		// Unlike "LANG" and "LC_*", "LANGUAGE" should not be assigned a complete locale name including the encoding part (e.g. ".UTF-8").
+		putenv("LANG=".$lang);
+		putenv("LANGUAGE=".preg_replace("/\.utf-?8/i", "", $lang));
+
+		setlocale(LC_ALL, $lang);
+
+		bind_textdomain_codeset('phpipam', 'UTF-8');
+		bindtextdomain("phpipam", dirname(__FILE__)."/locale");
+		textdomain("phpipam");
+
+		return true;
+	}
+
+	return false;
+}
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