Php coding question

[Chris8]

I'm messing with bbcodes and I have a little problem here.
What will be output of this:

preg_replace('/\{option(\d+)\}/e', "'%' . (intval('\\1')+1) . '\$s'", $bbcode['html']);

It supposed to replace {option1} {option2} {option3} and so on but to what exactly?

The default {option} is replaced with %2$s the above must have something in common with %2$s but I'm not sure how it's transformed.

Please help me to resolve this problem.