Like the commentor say, couldn’t you use WP_Query
for this?
$results = new WP_Query(array(
'post_type' => 'products',
'meta_query' => array(
'key' => 'availability',
'value' => $MyDate_a,
'compare' => '='
),
'order' => 'DESC',
'orderby' => 'meta_value'
));