Best practice way to delete user meta data during plugin uninstall?

Question

If a plugin stores data in the usermeta tables what is the best practice method to delete these entries for all users in uninstall.php? I could access the database directly but is there another way?

Answer 1

It's best not to interact with the database directly, especially when issuing DELETE statements, since a single typo can destroy unintended data. Instead, use WordPress functions to get a list of all user IDs, then remove the user meta field for each user individually, like so:

$all_user_ids = get_users( 'fields=ID' );
foreach ( $all_user_ids as $user_id ) {
    delete_user_meta( $user_id, 'your_meta_key_to_delete' );
}

Function reference:

http://codex.wordpress.org/Function_Reference/get_users http://codex.wordpress.org/Function_Reference/delete_user_meta

Answer 2

Best practice is to prefix the meta data your plugin enters that way you can simply do something like a search for all meta_key's like this

$wpdb->query( 
    $wpdb->prepare( 
        "
        DELETE FROM $wpdb->usermeta
        WHERE meta_key LIKE `_prefix_%`
        "
        )
);