Array not separating category ids in WordPress 'tax_query'

Question

I have the following code and its not working because the array is not responding as expected. I am creating category selection on WordPress metabox and stored in the database as serialized data but when using tax_query to fetch the selected categories, the array fails for separated the category id in the terms field. Check the code below:

$selected_categories = get_post_meta($post->ID, $prefix . 'services_category', true);
if ($selected_categories != '') {
    $categories = unserialize(get_post_custom($post->ID)[$prefix . 'services_category'][0]);
}

$cat_query = '';
$cat_query =  ( !empty($categories) ) ? implode(',', $categories) : '';

if ($cat_query != '') {
    $tax_query = array(
            array(
            'taxonomy' => 'services_cat',
            'field' => 'id',
            'terms' => array($cat_query),
            ),
        );
} else { $tax_query = null; }




$services_paged = is_front_page() ? get_query_var( 'page' ) : get_query_var( 'paged' );
query_posts(array(
    'post_type' => 'mt-services',
    'posts_per_page' => $services,
    'paged' => $services_paged,
    'tax_query' => $tax_query
));

Here is where my question lies: I'm trying to echo the selected categories from metabox but unfortunately they are all echoed as one item.

'terms' => array($cat_query)

Here's the result:

print_r(array($cat_query) 

gives me

Array ( [0] => 73,72 )

instead of

Array ( [0] => 73, [1] => 72 )

Detailed explanation

$categories values are 73 and 72.

Using implode function we get $cat_query which is (73,72) .

Hence the array($cat_query) would be array(73,72) which when printed out should be:

Array ( [0] => 73, [1] => 72 )

But instead, $cat_query values are taken as a unit which ends up being printed out as:

Array ( [0] => 73,72 )

which is wrong

Answer 1

$cat_query is created from $categories with the function implode. So I assume that $categories is an array that looks like the one you want:

Array ( [0] => 73, [1] => 72 )