what is #'s meaning in Reg?

[perfume]

$user_sig = preg_replace('#(<)([\/]?.*?)(>)#is', '&lt;\2&gt;', $user_sig

i dunno much bout regular expressions?
can u tell me how the sharp(#) works and what does the '\2' mean?
thx

[laserlight]

In this case the # symbol is used as the pattern delimiters. The \2 refers to the 2nd backreference.

I suggest that you read up on PCRE.