Regex to conditionally replace Twitter hashtags with hyperlinks

Question

I\'m writing a small PHP script to grab the latest half dozen Twitter status updates from a user feed and format them for display on a webpage. As part of this I need a rege

Answer 1

(^|\s)#(\w*[a-zA-Z_]+\w*)

PHP

$strTweet = preg_replace('/(^|\s)#(\w*[a-zA-Z_]+\w*)/', '\1#\2', $strTweet);

This regular expression says a # followed by 0 or more characters [a-zA-Z0-9_], followed by an alphabetic character or an underscore (1 or more), followed by 0 or more word characters.

http://rubular.com/r/opNX6qC4sG <- test it here.