Regex to match content inside @{...} construct with bracket balancing

Question

I want to create a regular expression that captures text between @{ some text }. I know how to do it for simple string, but in this case the text between the @{ } might contain starting and ending curly braces which will be confused with the braces in @{ }.

Example:

Input string:

This is some text that does not match the regex

@{

    This is some text

    {
        This another text

        {
            inner text
        }
    }

}

@{
    this is text2
}

another text that does not match the regex


@{
    this is another text
    {
        another inner text
    }
}

The result (3 matches) should be:

First match:

This is some text

{
    This another text

    {
        inner text
    }
}

Second match:

this is text2

Third match:

this is another text
{
    another inner text
}

Can anybody tell me how to achieve this? I'm using PHP by the way.

There are a lot of questions about how to match nested brackets with a regex in php. A little search will give you the answer. — Casimir et Hippolyte, Aug 23 '15 at 11:39
You can read about subroutine calls [here](http://regular-expressions.info/subroutine.html). — Wiktor Stribiżew, Aug 23 '15 at 11:40
possible duplicate of [Regex to get string between curly braces "{I want what's between the curly braces}"](http://stackoverflow.com/questions/413071/regex-to-get-string-between-curly-braces-i-want-whats-between-the-curly-brace) — l'L'l, Aug 23 '15 at 12:10
@l'L'l this is not what I'm looking for, I updated my examples to describe what I want. — m2008m1033m, Aug 23 '15 at 12:19
Wanting something and trying something are two different things, I recommend the latter since this isn't a "code my stuff for free" site. — l'L'l, Aug 23 '15 at 12:24
@l'L'l: I disagree with the duplicate target, since the question you suggest doesn't have a proper solution for arbitrarily nested brackets. — nhahtdh, Aug 24 '15 at 02:44

score 2 · Accepted Answer · edited May 23 '17 at 12:15

2

Probably need a recursive regex to solve the nested braces:

if(preg_match_all('/@(?={)([^}{]+|{((?1)*)})/', $str, $out)!==false)
  print_r($out[2]);

@(?={) starts at @ if followed by an opening brace
[^}{] matches any character that is not a brace
At (?1) is pasted from first parenthesized subpattern
((?1)*) captures wanted stuff to second group

See test at regex101, test at eval.in, SO regex FAQ if interested :]

edited May 23 '17 at 12:15

Community

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answered Aug 23 '15 at 12:21

Jonny 5

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Thanks a lot, that's exactly what I'm trying to accomplish :) – m2008m1033m Aug 23 '15 at 12:28
Hi, I have a similar question and tried to modify your answer to work in my situation but can't get it working. Would you mind taking a look? http://stackoverflow.com/questions/33218671/recursive-handling-of-nested-curly-braces-with-regex-for-cms – SISYN Oct 19 '15 at 22:01
@DanL - If you _undelete_ that question, I can post an answer for you. – Oct 19 '15 at 23:46

Regex to match content inside @{...} construct with bracket balancing

1 Answers1