I think I figured it out after looking a little harder at some of @kory’s posts.
Here’s what I did:
$query = array(
'post_type' => 'listing’,
'post_status' => 'publish',
'orderby' => 'date',
'order' => 'DESC',
'meta_query' => array(
'relation' => 'AND',
array(
'key' => 'ffd_status',
'value' => 'Closed',
'operator' => 'NOT IN',
),
array(
'key' => 'ffd_listingtype',
'value' => 'Sale',
'operator' => 'IN',
),
),
);
var_dump( http_build_query( $query ) );
Here’s the output:
post_type=listing&post_status=publish&orderby=date&order=DESC&meta_query%5Brelation%5D=AND&meta_query%5B0%5D%5Bkey%5D=ffd_status&meta_query%5B0%5D%5Bvalue%5D=Closed&meta_query%5B0%5D%5Boperator%5D=NOT+IN&meta_query%5B1%5D%5Bkey%5D=ffd_listingtype&meta_query%5B1%5D%5Bvalue%5D=Sale&meta_query%5B1%5D%5Boperator%5D=IN