Event query with all age group conditions
// WP_Query arguments
$args = array(
'post_type' => array( 'event' ),
'post_status' => array( 'publish' ),
'meta_query' => array(
'relation' => 'OR',
array(
array(
'key' => 'age_group_from',
'value' => '$ageMin',
'compare' => '<=',
),
),
array(
array(
'key' => 'age_group_to',
'value' => '$ageMax',
'compare' => '>=',
),
),
array(
'relation' => 'AND',
array(
'key' => 'age_group_to',
'compare' => 'NOT EXISTS',
),
array(
'key' => 'age_group_to',
'compare' => 'NOT EXISTS',
),
),
),
);
// The Query
$query = new WP_Query( $args );