Description:
------------
When working on a chat command system for a project, I was reading up on PCRE to properly build a robust command match regex. I read up that PCRE2 supports Replacement String Conditional be using ${1:+matched:unmatched}.
Ref: https://www.regular-expressions.info/replaceconditional.html#pcre2

I checked if PHP supported PCRE2 where I found a merged RFC PHP 7.3 about the topic. After testing my method, the conditional was not being parsed.

Test script:
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<?php
$message = "ban bob 24 days";
$regex = '/\{((?:(?!\d)\w)+?):?(?:(?<=\:)([[:graph:]]+))?\}/';
$commandPattern = "ban {name:\w+} {duration}";

$pattern = str_replace('/', '\/', $commandPattern);
$regex = '/^'.preg_replace($regex, '(?<$1>${2:-.*})', $pattern).' ?/miu';
echo $regex.PHP_EOL;

$regexMatched = (bool)preg_match($regex, $message, $matches);
var_dump($regexMatched, $matches);

Expected result:
----------------
/^ban (?<name>\w+) (?<duration>.*) ?/miu
bool(true)

array(5) { 
    [0]=> string(15) "ban bob 24 days" 
    ["name"]=> string(3) "bob" 
    [1]=> string(3) "bob" 
    ["duration"]=> string(7) "24 days" 
    [2]=> string(7) "24 days"
}


Actual result:
--------------
/^ban (?<name>${2:-.*}) (?<duration>${2:-.*}) ?/miu
bool(false)
array(0) {
}