Fires immediately before meta of a specific type is added.
Description
The dynamic portion of the hook name, $meta_type, refers to the meta object type (blog, post, comment, term, user, or any other type with an associated meta table). Possible hook names include: <ul> <li>add_blog_meta</li> <li>add_post_meta</li> <li>add_comment_meta</li> <li>add_term_meta</li> <li>add_user_meta</li> </ul>