Question

I’m having some difficulty with preg_match. I’m trying to match roman numerals, like this:

$string='This is roman XI and some other ones: XMCIII, like this.XXVIII'."\n";

preg_match('/(\s|\.)M{0,4}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})\s/',$string,$matches);

print_r($matches);

It should match any roman numeral preceded with whitespace or period and ending with whitespace. But it returns the following:

Array
(
    [0] =>  XI
    [1] =>
    [2] =>
    [3] => X
    [4] => I
)

Answer 1

You have {0, 4} or {0,3} ranges in regex which means that those parts are optional. You get spaces because space[nothing]space becomes a valid match.

You can simply filter out the empty space results from your array using array_filter