Check whether post is in a list of categories

Hi all

I had this line of code in a plugin I am developing:

if in_category($the_categories) { ... }

This works fine as long as $the_categories is something like “7” or “1001”. But as soon as it is a list of categories, like “7,1001”, it does not work any more.

So, how do I achieve this? Note that I cannot use

if (in_category($category1) || in_category($category2) )

…because I want to build a widget where the user can input a list of categories like “7,1001” (which then is used for the conditional tag.

Thanks!