As documented, you can set the compare
property of the meta query to NOT EXISTS
:
$args['meta_query'] = array(
array(
'key' => 'instrument',
'compare' => 'NOT EXISTS',
),
);
As documented, you can set the compare
property of the meta query to NOT EXISTS
:
$args['meta_query'] = array(
array(
'key' => 'instrument',
'compare' => 'NOT EXISTS',
),
);