PHP and JavaScript Localization

l10n.php

<?php
$g_default_lang = "en";
$g_messages = array();

function get_target_language() {
  global $g_default_lang;

  if (isset($_GET['lang'])) {
    return $_GET['lang'];
  }

  if (!isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
    return $g_default_lang;
  }

  $lang_list = $_SERVER['HTTP_ACCEPT_LANGUAGE'];

  $langs = array();
  $lang_ranges = explode(',', trim($lang_list));
  foreach ($lang_ranges as $lang_range) {
    if (preg_match('/(\*|[a-zA-Z0-9]{1,8}(?:-[a-zA-Z0-9]{1,8})*)(?:\s*;\s*q\s*=\s*(0(?:\.\d{0,3})|1(?:\.0{0,3})))?/', trim($lang_range), $match)) {
      if (!isset($match[2])) {
        $match[2] = '1.0';
      } else {
        $match[2] = (string) floatval($match[2]);
      }
      if (!isset($langs[$match[2]])) {
        $langs[$match[2]] = array();
      }
      $langs[$match[2]][] = $match[1];
    }
  }
  if (empty($langs)) {
    return $g_default_lang;
  }
  krsort($langs);
  return array_shift(array_shift($langs));
}

function setup_l10n($lang) {
  global $g_default_lang;

  // Read default language.
    $json = file_get_contents("_locales/$g_default_lang/messages.json");
  if ($json === FALSE) {
    return FALSE;
  }
  $dict = json_decode($json);

  // Read target language.
  $lang = str_replace("-", "_", $lang);
  $json = file_get_contents("_locales/$lang/messages.json");
  if ($json === FALSE) {
    $lang = array_shift(explode("_", $lang));
    $json = file_get_contents("_locales/$lang/messages.json");
  }
  if ($json !== FALSE) {
    $tmp = json_decode($json);
    foreach ($tmp as $key => $value) {
      $dict->$key = $value;
    }
  }
  $json = json_encode($dict);
  return array($dict, $json);
}

function _m($key) {
  global $g_messages;
  if (array_key_exists($key, $g_messages)) {
    return $g_messages->$key->message;
  }
  return $key;
}

$lang = get_target_language();
$result = setup_l10n($lang);
if ($result !== FALSE) {
  $g_messages = $result[0];
  echo "<script>\n";
  echo "var g_messages = " . rtrim($result[1]) . ";\n";
  echo "\n";
  echo <<<EOT
function _m(key) {
  if (key in g_messages) {
    return g_messages[key].message;
  }
  return key;
}

EOT;
  echo "</script>\n";
}