Regex between tags unless escaped

Question

I made a PHP wrapper around Pygments library that highlights code blocks. Regex used for codeblocks detection can be configured in configuration file. (json for

Answer 1

What you need is a rather tricky regex feature called a "zero-width negative look-behind assertion". "Zero-width" meaning it matches zero characters of the input, "negative" meaning it succeeds only if it is not found, and "look-behind" meaning it looks backwards.

The syntax for this is (?<!test) where test is the thing you want to not be there.

In your case, you want to match a [ but ignore it if preceded by a \, both of which need escaping, so you need (?<!\\)\[

So your regex ends up as (in PHP) $re = '/(?<!\\\\)\[pygments=(.*?)\](.*?)\[\/pygments\]/';

According to json_encode, that then ends up as "\/(?<!\\\\)\\[pygments=(.*?)\\](.*?)\\[\\\/pygments\\]\/" in JSON. I think my eyes are beginning to go funny with all the backslashes... ;)