Update PMPro member and order searches to also search by discount code.

discount_code_search_for_pmpro_members_list.php

/**
 * Update member and order searches to also search by discount code.
 *
 * I'm not recommending anyone actually use this, but sharing as an example.
 *
 * This is a little hacky how the members list SQL is edited.
 * You get odd results if you change the level or other parameters
 * on the members list table and also search for an order.
 * Can also act wonky if you have overlaps between your discount code names
 * and cities, user names, names, or anything else that would normally
 * score a hit for a search.
 */
function discount_code_search_for_pmpro_members_list( $sqlQuery ) {
	global $wpdb;
	
	if(isset($_REQUEST['s']))
		$s = sanitize_text_field(trim($_REQUEST['s']));
	else
		$s = "";
		
	// is this a discount code?
	$code = $wpdb->get_row( "SELECT * FROM $wpdb->pmpro_discount_codes WHERE code = '" . esc_sql( $s ) . "' LIMIT 1" );
	
	if ( ! empty( $code ) ) {
		// Get user's using this code
		$user_ids_uses = $wpdb->get_col( "SELECT DISTINCT(user_id) FROM $wpdb->pmpro_discount_codes_uses WHERE code_id = '" . esc_sql( $code->id ) . "'");
		
		$user_ids_users = $wpdb->get_col( "SELECT DISTINCT(user_id) FROM $wpdb->pmpro_memberships_users WHERE code_id = '" . esc_sql( $code->id ) . "'");
		
		$user_ids = array_unique( array_merge( $user_ids_uses, $user_ids_users ) );
		
		if ( ! empty( $user_ids ) ) {
			$sql_to_match = "WHERE mu.membership_id > 0 AND ";
			$sql_to_swap = "WHERE mu.membership_id > 0 AND mu.user_id IN(" . implode( ',', $user_ids ) . ") OR ";
			$sqlQuery = str_replace( $sql_to_match, $sql_to_swap, $sqlQuery );
		}
	}
	
	return $sqlQuery;
}
add_filter( 'pmpro_members_list_sql', 'discount_code_search_for_pmpro_members_list' );