WP_Query 'meta_query' for "Date Start" and "Date End" custom fields. Conditions are (relation = 'OR'):
<?php
/**
* WP_Query 'meta_query' for "Date Start" and "Date End" custom fields.
* Conditions are (relation = 'OR'):
* 1. If "Date End" does not exist, compare "Date Start" only.
* 2. If "Date End" exists, show events in between that and "Date Start".
*/
'meta_query' => array(
'relation' => 'OR',
array(
'key' => 'date_start',
'value' => date( 'Ymd' ),
'compare' => '=',
'type' => 'date'
),
array(
'relation' => 'AND',
array(
'key' => 'date_start',
'value' => date( 'Ymd' ),
'compare' => '<=',
'type' => 'date'
),
array(
'key' => 'date_end',
'value' => date( 'Ymd' ),
'compare' => '>=',
'type' => 'date'
),
),
)