What does \\0 means?

From:	Jay	Date:	Thu, 05 Aug 2004 11:39:52 +0000
Subject:	What does \\0 means?
Groups:	php.general
Request:	Send a blank email to php-general+get-192833@lists.php.net to get a copy of this message

Hi! Found the following code in the PHP manual: $text = "http://www.somelink.com"; echo(ereg_replace("[[:alpha:]]+://[^<>[:space:]]+[[:alnum:]/]",

                    "<a href=\"\\0\">\\0</a>", $text));

What does \\0 means, i have seen this before with \\1 and \\2 what does they mean? Thanx In Advance Jay