sorry, PHP build-in fonts dont support russian letters. But you still have two choses:
1) very painfull but has the best result: use imagettftext() function instead of imagestring(), which uses a font u specify (even .ttf font from windows would work on unix systems). This method is painfull, because u'll have to make lots of other changes to the code besides that...
2) easy one: convert all russian letter to translit (а = a, я = ya, д = d, etc)
If the second chose would succesfy u, then insert on top of the signature.php this:function translit($text) {
$array = array("а","б","в","г","д","е","ё","ж","з","и","й","к","л","м","н","о","п","р","с","т","у","ф","х","ц","ч","ш","щ","ь","ъ","э","ю","я","ы","А","Б","В","Г","Д","Е","Ё","Ж","З","И","Й","К","Л","М","Н","О","П","Р","С","Т","У","Ф","Х","Ц","Ч","Ш","Щ","Ь","Ъ","Э","Ю","Я","Ы");
$array_tr = array("a","b","v","g","d","e","e","zh","z","i","j","k","l","m","n","o","p","r","s","t","u","f","h","c","ch","sh","shj","'","j","e","yu","ya","y","A","B","V","G","D","E","E","Zh","Z","I","J","K","L","M","N","O","P","R","S","T","U","F","H","C","Ch","Sh","Shj","'","J","E","Yu","Ya","Y");
return str_replace($array, $array_tr, $text);
}
Then, any text u need to convert, send it through translit() function.
For example, for "last registered user" replace array(array($fsize, $offset2+$tiny, $lang_new_user, "text_color"), array($fsize, $far, $show['new_user'], "text_color"))
with: array(array($fsize, $offset2+$tiny, $lang_new_user, "text_color"), array($fsize, $far, translit($show['new_user']), "text_color"))
Good luck.