how to get the post/page ID in widget

Hi,

You can use like below:

$post_id = $GLOBALS[‘post’]->ID;

Very close to my need !

I’m looking for this for category without post_id defined.

Any solution ?

If you are trying to display the category id for all/one category look at Function_Reference/get_categories.

If in admin you are looking for the id see:
How do I determine a Post, Page, Category, Tag, Link, Link Category, or User ID?