Perform cleanup tasks.
This hook is run at the end of most regular page requests. It is often used for page logging and specialized cleanup. This hook MUST NOT print anything because by the time it runs the response is already sent to the browser.
Only use this hook if your code must run even for cached page views. If you have code which must run once on all non-cached pages, use hook_init() instead. That is the usual case. If you implement this hook and see an error like 'Call to undefined function', it is likely that you are depending on the presence of a module which has not been loaded yet. It is not loaded because Drupal is still in bootstrap mode.
$destination: If this hook is invoked as part of a drupal_goto() call, then this argument will be a fully-qualified URL that is the destination of the redirect.
Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.
function hook_exit($destination = NULL) {
db_update('counter')
->expression('hits', 'hits + 1')
->condition('type', 1)
->execute();
}