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Introduction

The Metadata API that can be used to retrieve and manipulate meta data, regardless of the 'type' of meta data; located in /wp-includes/meta.php (code). WordPress stores the comment, post, and user meta data types in the WordPress database.

Note: This information applies to WordPress Version 2.9 and higher. Before Version 2.9, meta data was only handled by functions unique to the meta_type.

Meta Data Functions

add_metadata($meta_type, $object_id, $meta_key, $meta_value, $unique = false) Adds metadata to a table. Must define either $meta_type or $meta_key to return something.

Parameters

$meta_type (String - Possible Values: user, comment, post)

$object_id (Integer - {$meta_type}_id: ID of current object)

$meta_key (String - value assigned to key)

$meta_value (String - value assigned to object/key pair)

$unique (Boolean - If set to true, the specified meta key already exists, the function returns false and makes no changes; otherwise, it returns true.)

Parameters include: type ('comment', 'post', 'user', etc), the ID of the content, the meta data key/value pair and determines if the information must be unique (true or false).

delete_metadata($meta_type, $object_id, $meta_key, $meta_value = , $delete_all = false) Removes metadata from a table.

get_metadata($meta_type, $object_id, $meta_key = , $single = false) Retrieves metadata 'value' for the specified 'type', 'object ID', and 'key' for ***.

update_meta_cache($meta_type, $object_ids) Updates metadata cache for the specified 'type' and 'object ID'.

_get_meta_table($type) Retrieves all metadata key/value pairs based on the specified 'type' (e.g 'user').

Reference: Meta Data Types

• Posts
• Users
• Comments

Function Reference