ElasticSearch and searching on multiple fields in PHP

I am using the latest version of elasticsearch-php as well as the latest version of MongoDB and ElasticSearch.

I need to do a search on multiple fields that can contain one or multiple values. Example:

country_code should be either NL, BE or DE AND category should contain be AA01, BB01, CC02 or ZZ11

I thought I would solve it as followed (PHP):

$countries = array(“NL”, “BE”, “DE”);
$category = array(“AA01”, “BB01”, “CC02”, “ZZ11”);

$searchParams['body']['query']['bool']['must']['terms']['country'] = $countries;
$searchParams['body']['query']['bool']['must']['terms']['categories'] = $category;
$searchParams['body']['query']['bool']['must']['terms']['minimum_should_match'] = 1;

But the result does not even come close the the data that I expect to get back.

Sometimes $countries and/or $category can only have one element.