Транслитерация текста с помощью php

<?php
function transliterate_text($tt)
{
    $tt = strtr($tt, array('а'=>'a','А'=>'A','б'=>'b','Б'=>'B',
    'в'=>'v','В'=>'V','г'=>'g','Г'=>'G','д'=>'d','Д'=>'D',
    'е'=>'e','Е'=>'E','ё'=>'e','Ё'=>'E','ж'=>'zh','Ж'=>'ZH',
    'з'=>'z','З'=>'Z','и'=>'i','И'=>'I','й'=>'y','Й'=>'Y',
    'к'=>'k','К'=>'K','л'=>'l','Л'=>'L','м'=>'m','М'=>'M',
    'н'=>'n','Н'=>'N','о'=>'o','О'=>'O','п'=>'p','П'=>'P',
    'р'=>'r','Р'=>'R','с'=>'s','С'=>'S','т'=>'t','Т'=>'T',
    'у'=>'u','У'=>'U','ф'=>'f','Ф'=>'F','х'=>'h','Х'=>'H',
    'ц'=>'ts','Ц'=>'TS','ч'=>'ch','Ч'=>'CH','ш'=>'sh',
    'Ш'=>'SH','щ'=>'shch','Щ'=>'SHCH','ъ'=>'','Ъ'=>'','ы'=>'i',
    'Ы'=>'I','ь'=>''','Ь'=>''','э'=>'e','Э'=>'E','ю'=>'yu',
    'Ю'=>'YU','я'=>'ya','Я'=>'YA')); 
    return $tt;
}
$line = 'Привет, мир!';
echo transliterate_text($line);
?>