Is this the shortest way to convert to roman numerals? I think so.

roman-numerals.php

<?php
// i woke up this morning with the
// odd thought that i want to
// find out what's the most optimal
// way to spell out an integer as
// roman numerals is.
function romanChar(&$num,$value,$code)
{
  $r = "";
  while($num >= $value)
  {
    $num -= $value;
    $r .= $code;
  }
  return $r;
}
function roman($num)
{
  $r .= romanChar($num,1000,"M");
  $r .= romanChar($num,900,"CM");
  $r .= romanChar($num,500,"D");
  $r .= romanChar($num,400,"CD");
  $r .= romanChar($num,100,"C");
  $r .= romanChar($num,90,"XC");
  $r .= romanChar($num,50,"L");
  $r .= romanChar($num,40,"XL");
  $r .= romanChar($num,10,"X");
  $r .= romanChar($num,5,"V");
  $r .= romanChar($num,4,"IV");
  $r .= romanChar($num,1,"I");
  return $r;
}

// test
for ($x=0; $x<10; $x++)
{
  $n = rand(0,4000);
  printf("%4d - %s\n",$n,roman($n));
}
?>