add_(meta_type)_meta action-hook . WP 3.1.0

Fires immediately before meta of a specific type is added.

The dynamic portion of the hook, $meta_type, refers to the meta object type (comment, post, term, or user).

Usage

add_action( 'add_(meta_type)_meta', 'action_function_name_8148', 10, 3 );
function action_function_name_8148( $object_id, $meta_key, $_meta_value ){
	// action...
}

$object_id(int)

Object ID.

$meta_key(string)

Meta key.

$_meta_value(mixed)

Meta value.

Where the hook is called

do_action( "add_{$meta_type}_meta", $object_id, $meta_key, $_meta_value );

Where the hook is used (in WP core)