Roman numerals to numbers in string - php

Question

I have this string:
$string = 'Hello IV WorldX';
And I want to replace all roman numerals to integers.
I have the following function to convert roman to integer:
function roman2number($roman){
$conv = array(
array("letter" => 'I', "number" => 1),
array("letter" => 'V', "number" => 5),
array("letter" => 'X', "number" => 10),
array("letter" => 'L', "number" => 50),
array("letter" => 'C', "number" => 100),
array("letter" => 'D', "number" => 500),
array("letter" => 'M', "number" => 1000),
array("letter" => 0, "number" => 0)
);
$arabic = 0;
$state = 0;
$sidx = 0;
$len = strlen($roman);
while ($len >= 0) {
$i = 0;
$sidx = $len;
while ($conv[$i]['number'] > 0) {
if (strtoupper(#$roman[$sidx]) == $conv[$i]['letter']) {
if ($state > $conv[$i]['number']) {
$arabic -= $conv[$i]['number'];
} else {
$arabic += $conv[$i]['number'];
$state = $conv[$i]['number'];
}
}
$i++;
}
$len--;
}
return($arabic);
}
echo roman2number('IV');
Works great (try it on ideone). How do I search & replace through the string to replace all instances of roman numerals. Something like:
$string = romans_to_numbers_in_string($string);
Sounds like regex needs to come to the rescue... or?

Answer 1

Here's a simple regex to match roman numerals:
\b[0IVXLCDM]+\b
So, you can implement romans_to_numbers_in_string like this:
function romans_to_numbers_in_string($string) {
return preg_replace_callback('/\b[0IVXLCDM]+\b/', function($m) {
return roman2number($m[0]);
},$string);
}
There are some problems with this regex. Like, if you have a string like this:
I like roman numerals
It will become:
1 like roman numerals
Depending on your requirements, you can let it be, or you can modify the regex so that it doesn't convert single I's to numbers.