Retrieves raw metadata value for the specified object.

Returns the object subtype for a given object ID of a specific type.

Retrieves a list of registered meta keys for an object type.

Retrieves registered metadata for a specified object.

Determines whether a meta key is considered protected.

Determines if a meta field with the given key exists for the given object ID.

Registers a meta key.

Checks if a meta key is registered.

Sanitizes meta value.

Unregisters a meta key from the list of registered keys.