preg_replace help

[LemonInflux]

I'm trying to make sense of the BBCode tutorial on this website, and someone told me I should just look at how the regex is constructed, and follow suit. So, will someone please explain to me A) what this is, and B) how  to make it work:

 

<?php
$data = preg_replace("`[b](.*)[/b]`sUi","<b>\1</b>",$data);
?>

if I use that, and put [b]anything[/b], it doesn't work.

[Demonic]

Try:

 

<?php
$data = preg_replace("/\[b\](.*)\[\/b\]/si","<b>$1</b>",$data);
?>