One of the things that we have being discussing for a very long time is extending WordPress with a comment meta api or even the idea of a generic meta api for WordPress and indeed this is something we are discussing at the moment and I thought I would jot down some thoughts on what I would like to see from an API point of view.  Over the weekend at WordCamp UK we also heard about situations where some people are already adding comment meta tables for plugin usage and so the demand is definitely there.

I don’t really care how the data is stored, be it single table or multi table, all I care about is having a good stable API for plugins and the core to work with.  If the API is good and well thought out they don’t need to care about the table structure and we can always change it later.

Therefore I thought I would summarise the features I would like to see in a generic meta api:

• Flexibility to easily create a different kind of meta without having to care about adding tables yourself.
• Ability to store anything in a meta value – i.e. The same kind of functionality we have we options.
• Ability to get things back based on key ranges or operations – i.e. Getting all cron meta values where the meta key (which would be a timestamp) is before a particular time.

So I am thinking of an api like this:

/*
* Register a new meta type.
* If we have a table per meta this will create the table for you if required
*/
register_meta_type('cron');

/*
* Returns the meta value for a particular key
*/
get_meta_value('cron', $key);

/*
* Sets the meta value for a particular key
*/
set_meta_value('cron', $key, $value);

/*
* Returns the meta values for a particular key based search
*/
get_meta_values('cron', $search_value, $search_type);

/*
* Deletes the meta value for a particular key
*/
delete_meta_value('cron', $key);

I would envisage us enabling the use of the new api with wrapper functions for different meta types as required. These wrapper functions would only be included if required, for example we could create a comment_meta wrapper api around these generic meta api functions which would only be available if a plugin / theme called enable_comment_meta_api()