post_rank
$meta_query = array( 'relation' => 'OR', array( 'key' => 'post_rank', 'value' => '1', 'compare' => '=', ), array( 'key' => 'post_rank', 'value' => '2', 'compare' => '=', ), );
$meta_query = array( 'relation' => 'OR', array( 'key' => 'post_rank', 'value' => '1', 'compare' => '=', ), array( 'key' => 'post_rank', 'value' => '2', 'compare' => '=', ), );