Metadata (category)

add_metadata()

Add metadata (an additional data) for the specified object (a post, a comment, a user etc).

delete_metadata()

Delete metadata for the specified object.

delete_metadata_by_mid()

Delete meta data by meta ID

get_metadata()

Retrieve metadata for the specified object.

is_protected_meta()

Determines whether a meta key is protected (internal).

register_meta()

Registers a meta key (key of custom field).

sanitize_meta()

Sanitize meta value.

update_metadata()

Update metadata for the specified object. If no value already exists, the metadata will be added as new metadata.