可以在正则表达式匹配中使用$ 1吗？

Question

I'm creating a text parser, that basically looks for the following:

{IF SOMETHING} then include this text {ENDIF SOMETHING}

I can find that by using the regex:

/{IF [A-Z]+}.*{ENDIF [A-Z]}/

But that wont help if there are nested conditions. So i was looking to do something more like:

/{IF ([A-Z]+)}.*{ENDIF $1}/

But that doesn't seem to work - is it possible?

Answer 1

You can use this other syntax too: \\g{1} that is useful to avoid confusion with a backreference followed with a literal digit. This syntax allows to use relative references like this: \\g{-1} (ie the last defined capture group on the left)

$1 is only used in a replacement string with preg_replace .

Answer 2

PHP Regex uses \\1 instead of $1. For more information, refer to the PHP Manual on regex back references.