Get entry ID within plugin controller
A field in Craft can belong to any element (entry, tag, category, user, etc.).

If you want to get the ID of the element the field may or may not be currently attached to, you can do this from your Field Type class:

$elementId = isset($this-&gt;element) ? $this-&gt;element-&gt;id : null;

if ($elementId)
{
    ...
}