Extract multiples strings from one variable by using preg_match

I'm having troubles extracting several strings between tags from a variable, in order to echo them inside a span individually.
Thing is, the tags in question are determined by a variable, here is what it looks like :

<?php
    $string = "[en_UK]english1[/en_UK][en_UK]english2[/en_UK][fr_FR]francais1[/fr_FR][fr_FR]francais2[/fr_FR][fr_FR]francais3[/fr_FR]";
    $lang = "en_UK";

    preg_match("/(.[$lang]), (.[\/$lang])/", $string, $outputs_list);

    foreach ($outputs_list as $output) {
        echo "<span>".$output."/span>";
    }

    // in this exemple I want to output :
    // <span>english1</span>
    // <span>english2</span>
?>

It's my first time using preg_match and after trying so many differents things I'm kinda lost right now.
Basically I want to extract every strings contained between the tags [$lang] and [/$lang] (in my exemple $lang = "en_UK" but it will be determined by the user's cookies.

I'd like some help figuring this out if possible,

Thanks

Solution

[] in a regular expression makes a character class. I'm not sure what you're trying to do with the .s and , either. Your regex currently says:

Any single character, an e, n, _, U, or K, a , and space, and again any single character, an e, n, _, U, K, but this time also allowing /.

Regex demo: https://regex101.com/r/8pmy89/2

I also believe you were grouping the wrong value. The () go around what you want to capture, know as a capture group.

I think the regex you want is:

\[$lang\](.+?)\[\/$lang\]

Regex demo: https://regex101.com/r/8pmy89/3

PHP Usage:

$string = "[en_UK]english1[/en_UK][en_UK]english2[/en_UK][fr_FR]francais1[/fr_FR][fr_FR]francais2[/fr_FR][fr_FR]francais3[/fr_FR]";
$lang = "en_UK";
preg_match_all("/\[$lang\](.+?)\[\/$lang\]/", $string, $outputs_list);
foreach ($outputs_list[1] as $output) {
    echo "<span>".$output."/span>";
}

PHP demo: https://eval.in/686086

Preg_match vs. preg_match_all

Preg_match only returns the first match(es) of a regex. Preg_match_all returns all matches of the regex. The 0 index has what the full regex matched. All subsequent indexes are each capture groups, e.g. 1 is the first capture group.

Simple Demo: https://eval.in/686116

$string = '12345';
preg_match('/(\d)/', $string, $match);
print_r($match);
preg_match_all('/(\d)/', $string, $match);
print_r($match);

Output:

Array
(
    [0] => 1
    [1] => 1
)

^ is preg_match, below is the preg_match_all

Array
(
    [0] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
            [3] => 4
            [4] => 5
        )

    [1] => Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
            [3] => 4
            [4] => 5
        )

)