Date Time Php

Here's a little function I put together to convert an Arabic number between 0 and 9,999 to a
Roman Numeral. Initial testing went well, but it has not been fully tested yet.
function to_roman($num) {
// Function to convert an arabic number ($num) to a roman numeral. $num must be between
0 and 9,999
if ($num < 0 || $num > 9999) { return -1; } // out of range
$r_ones = array(1=> "I", 2=>"II", 3=>"III", 4=>"IV", 5=>"V", 6=>"VI", 7=>"VII", 8=>"VIII",
9=>"IX");
$r_tens = array(1=> "X", 2=>"XX", 3=>"XXX", 4=>"XL", 5=>"L", 6=>"LX", 7=>"LXX",
8=>"LXXX", 9=>"XC");
$r_hund = array(1=> "C", 2=>"CC", 3=>"CCC", 4=>"CD", 5=>"D", 6=>"DC", 7=>"DCC",
8=>"DCCC", 9=>"CM");
$r_thou = array(1=> "M", 2=>"MM", 3=>"MMM", 4=>"MMMM", 5=>"MMMMM", 6=>"MMMMMM",
7=>"MMMMMMM", 8=>"MMMMMMMM", 9=>"MMMMMMMMM");
$ones = $num % 10;
$tens = ($num - $ones) % 100;
$hundreds = ($num - $tens - $ones) % 1000;
$thou = ($num - $hundreds - $tens - $ones) % 10000;
$tens = $tens / 10;
$hundreds = $hundreds / 100;
$thou = $thou / 1000;
if ($thou) { $rnum .= $r_thou[$thou]; }
if ($hundreds) { $rnum .= $r_hund[$hundreds]; }
if ($tens) { $rnum .= $r_tens[$tens]; }
if ($ones) { $rnum .= $r_ones[$ones]; }
return $rnum;
} // function to_roman($num)
?>