<p>For those of us who use standard shared hosting packages, such as GoDaddy or Network Solutions, how do you handle datetime conversions when your hosting server (PHP) and MySQL server are in different time zones?</p>

<p>Also, does anybody have some best practice advice for determining what time zone a visitor to your site is in and manipulating a datetime variable appropriately?</p>

Store everything as UTC.  You can do conversions at the client level, or on the server side using client settings.
php - date
mysql - utc-timestamp