Why do PHP error messages contain a link, such as this error:

`<b>Warning</b>: preg_match_all() [<a href='function.preg-match-all'>function.preg-match-all</a>]: Delimiter must not be alphanumeric or backslash in <b>/home/www/test.php</b> on line <b>93</b><br />`

with this link?:

`[<a href='function.preg-match-all'>function.preg-match-all</a>]`

Is the assumption that PHP will be configured to put a `http://www.php.net/` in front of that URL? Or that a person will have a copy of the PHP documentation on their web server and that by clicking on that link they will be able to access information about the function?

This is just something I've been curious about since it seems that unless the error occurred on php.net, such a link would be useless.

I know it's possible to set up custom error handlers, etc. My question is: Why is this the default behavior of PHP?

Thanks.