PHP Plugin Error

[enci]

I am trying to place a php script on my board to track user information such as referer, query string, etc. I created a plugin and placed it in the parse_templates hook location. However, when I activate the plugin and test it, I see these errors in my error_log:

PHP Fatal error: Call to a member function query_read_slave() on a non-object in /path/to/board/includes/functions.php on line 2970

PHP Fatal error: Call to a member function shutdown_query() on a non-object in /path/to/board/showthread.php on line 490

PHP Fatal error: Call to a member function unlock_tables() on a non-object in /path/to/board/includes/functions.php on line 4998

I am pretty sure my php script works because I copied it directly from a working script.

Thanks.