Everyone caches, that's a pretty well known fact. However, the problem I always seemed to have was how to properly name my cache keys. After much trial and tribulation, I believe I have found a great way to properly name cache keys. To make things easy, my keys usually follow this format.
<model|table>__<function|method>[-<params>]
To clear up some confusion, it goes as follows. The first word of your cache key should be your model name (or database table name), as most cached data relates to a database query result. The model name is followed by a double underscore, which is then followed by the function/method name (which helps to identify exactly where the cache is set), which is then followed by multiple parameters (optional). Here's a quick example:
public function getUserProfile($id) {
$cacheKey = __CLASS__ .'__'. __FUNCTION__ .'-'. $id;
// Check the cache or query the database
// Cache the query result with the key
// Return the result
}
The $cacheKey above would become: User__getUserProfile-1337, assuming the user's ID is 1337. Pretty easy right? Besides the verbosity that it takes to write these constants, it works rather well (unless you want to write the method and class manually). You may also have noticed that I used __FUNCTION__ over __METHOD__ -- this was on purpose. The main reasoning is that __METHOD__ returns the class and method name, like User::getUserProfile, while __FUNCTION__ just returns the method name.
The example above will work in most cases, but there are other cases where something more creative is needed. The main difficulty is how to deal with array'd options. There are a few ways of dealing with that, the first is checking to see if an ID or limit is present, if so, use that as the unique value. If none of the options in the array are unique, you can implode/serialize the array and run an md5() on the string to create a unique value.
User::getTotalActive();
// User__getTotalActive
Topic::getPopularTopics($limit);
// Topic__getPopularTopics-15
Forum::getLatestActivity($id, $limit);
// Forum__getLatestActivity-1-15
Post::getAllByUser(array('user_id' => $user_id, 'limit' => $limit));
// Post__getAllByUser-1-15
User::searchUsers(array('orderBy' => 'username', 'orderDir' => 'DESC'));
// User__searchUsers-fcff339541b2240017e8d8b697b50f8b
In most cases an ID or query limit can be used as a unique identifier. If you have another way that you name your cache keys or an example where creating the key can be difficult, be sure to tell us about it!