regex not matching due to repeated capturing group rather than capturing a repeated group

Question

I have the following regexp:

/(?:[\\[\\{]*)(?:([A-G\\-][^A-G\\]\\}]*)+)(?:[\\]\\}]*)/

with the following expression:

{A\'\'         


        

Answer 1

You are trying to match repeated capturing groups and get the captures. It is not possible with PHP PCRE regex.

What you can do is to make sure you either extract all {...} / [...] substrings, trim them from the brackets and use a simple [A-G-][^A-G]* regex, or add a \G operator and make your regex unmaintainable but working as the original one.

Solution 1 is

/(?:[[{]*|(?!\A)\G)\K[A-G-][^A-G\]}]*/

See the regex demo. Note: this regex does not check for the closing ] or }, but it can be added with a positive lookahead.

• (?:[[{]*|(?!\A)\G) - matches a [ or {, zero or more occurreces, or the end location of the previous successful match
• \K - omits the text matched so far
• [A-G-] - letters from A to G and a -
• [^A-G\]}]*- zero or more chars other than A to G and other than ] and }.

See PHP demo.

Solution 2 is

$re = '/(?|{([^}]*)}|\[([^]]*)])/'; 
$str = "{A''BsCb}"; 
$res = array();
preg_match_all($re, $str, $m);
foreach ($m[1] as $match) {
    preg_match_all('~[A-G-][^A-G]*~', $match, $tmp);
    $res = array_merge($tmp, $res);
}
print_r($res);

See the PHP demo

The (?|{([^}]*)}|\[([^]]*)]) regex just matches strings like {...} or [...] (but not {...] or [...}) and captures the contents between brackets into Group 1 (since the branch reset group (?|...) resets the group IDs in each branch). Then, all we need is to grab what we need with a more coherent '~[A-G-][^A-G]*~' regex.