Checking to see if one array's elements are in another array in PHP

Question

I have two arrays in PHP as follows:

People:

Array
(
    [0] => 3
    [1] => 20
)

Wanted Criminals:

Answer 1

if 'empty' is not the best choice, what about this:

if (array_intersect($people, $criminals)) {...} //when found

or

if (!array_intersect($people, $criminals)) {...} //when not found