There are several high-traffic mailing lists available for PHP discussion. Please remember your netiquette when asking a question: be polite, offer as many examples you can (if you're describing a problem), provide your system information (if looking for a solution), and did I mention to say please and thank you?
A comprehensive mailing list subscription management tool for the PHP-related mailing lists can be found at http://www.php.net/mailing-lists.php. The English PHP mailing lists are archived and available for searching at http://marc.theaims-group.com/. Just look for the PHP-related lists under the "WWW" heading. An invaluable resource, which archives the MySQL mailing list as well as quite a few others!