php regex to extract single parameter value from string

I'm working with a string containing parameters, separated by some special characters in PHP with preg_match

An example could be like this one, which has four parameters.

1stparm?#?1111?@?2ndParm?#?2222?@?3rdParm?#?3333?@?4thparm?#?444?@?

Each parameter name is followed by ?#?, and its value is right next to it, ending with ?@? (note: values can be strings or numbers, and even special characters)

I've probably overcomplicated my regex, which works in SOME cases, but not if I search for the last parameter in the string..

This example returns 2222 as the correct value (in group 1) for 2ndParm

(?:.*)2ndParm\?#\?(.*?)\?@\?(?=.)(.*)

but it fails if 2ndParm is the last one in the string as in the following example:

1stparm?#?1111?@?2ndParm?#?2222?@?

I'd also appreciate help in just returning one group with my result.. i havent been able to do so, but since I always get the one I'm interested in group 1, I can get it easily anyway.

Solution

You can use

(?P<key>.+?)
\Q?#?\E
(?P<value>.+?)
\Q?@?\E

in verbose mode, see a demo on regex101.com.

The \Q...\E construct disables the ? and # "super-powers" (no need to escape them here).

In PHP this could be

<?php
$string = "1stparm?#?1111?@?2ndParm?#?2222?@?3rdParm?#?3333?@?4thparm?#?444?@?";

$regex = "~(?P<key>.+?)\Q?#?\E(?P<value>.+?)\Q?@?\E~";

preg_match_all($regex, $string, $matches, PREG_SET_ORDER);

foreach ($matches as $match) {
    echo $match["key"] . " = " . $match["value"] . "\n";
}

?>

Which yields

1stparm = 1111
2ndParm = 2222
3rdParm = 3333
4thparm = 444

Or shorter:

$result = array_map(
    function($x) {return array($x["key"] => $x["value"]);}, $matches);
print_r($result);