Remove multiple elements from a flat array using whitelisted values

I have an array like this:

$categories_array = ['category_1', 'category_2', 'category_3', 'category_4'];

I'd like to filter the array to get a new one. For example, I'd like to have a new array with only category_2 and category_3 and preserve the original keys like this:

$new_categories_array = [1 => 'category_2', 2 => 'category_3'];

See

• array_diff — Computes the difference of arrays
• array_intersect — Computes the intersection of arrays

Example:

$original = array('category_1','category_2','category_3','category_4');
$new      = array_diff($original, array('category_1', 'category_4'));

print_r($new);

Output:

Array
(
    [1] => category_2
    [2] => category_3
)

When using array_intersect the returned array would contain cat 1 and 4 obviously.