meta query
https://developer.wordpress.org/reference/classes/wp_meta_query/ $pattern = ""; 'meta_query' => array( array( 'key' => 'birthday', 'value' => $pattern, 'compare' => 'REGEXP' ), 'popularity_clause' => array( 'key' => 'subscription_count', 'compare' => 'EXISTS', 'type' => 'NUMERIC' ) ), 'orderby' => array( 'popularity_clause' => 'DESC', 'title' => 'ASC' ) 'meta_query' => array( array( 'key' => 'key-1', 'value' => $value, 'compare' => '=' ), 'x_clause' => array( 'key' => 'key-2', 'compare' => 'EXISTS' ) ), 'meta_ty