Regular expression to find and replace @ mentions like twitter

Question

I am developing a PHP application which needs a regular expression to replace the @ mentions like twitter. Also the regular expression should satisfy the following needs.

Answer 1

How about something like -

(?<!\w)@[\w]+

Answer 2

Wow. I found the answer myself guys.

$tweet = preg_replace('/(^|[^a-z0-9_])@([a-z0-9_]+)/i', '$1<a href="http://twitter.com/$2">@$2</a>', $tweet);

Thanks for your help guys.

Answer 3

As twitter can contain up to 15 characters, you could write it like this to avoid some bugs:

$tweet = preg_replace("/(^\w)@(\w{1,15})/i", "\\1<a ref=\"http://twitter.com/\\2\">@\\2</a>", $tweet);