Define custom delete behavior for this module's field data.
This hook is invoked from field_attach_delete() on the module that defines a field, during the process of deleting an entity object (node, taxonomy term, etc.). It is invoked just before the data for this field on the particular entity object is deleted from field storage. Only field modules that are storing or tracking information outside the standard field storage mechanism need to implement this hook.
$entity_type: The type of $entity.
$entity: The entity for the operation.
$field: The field structure for the operation.
$instance: The instance structure for $field on $entity's bundle.
$langcode: The language associated with $items.
$items: $entity->{$field['field_name']}[$langcode], or an empty array if unset.
Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.
function hook_field_delete($entity_type, $entity, $field, $instance, $langcode, &$items) {
foreach ($items as $delta => $item) {
// For hook_file_references(), remember that this is being deleted.
$item['file_field_name'] = $field['field_name'];
// Pass in the ID of the object that is being removed so all references can
// be counted in hook_file_references().
$item['file_field_type'] = $entity_type;
$item['file_field_id'] = $entity
->id();
file_field_delete_file($item, $field, $entity_type, $entity
->id());
}
}