经测试代码如下：
/**
* 阿拉伯数字转罗马数字
*
* @param
* @arrange (512.笔记) jb51.cc
**/
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)
/*** 代码来自编程之家 jb51.cc（jb51.cc） ***/