Automatically applies an EDD discount code if certain cart conditions are met.

edd-auto-apply-discount-code.php

<?php
/**
 * Plugin Name: EDD - Discounts for Subscribers
 * Plugin URI: https://www.nosegraze.com/apply-edd-discount-code-cart-contents
 * Description: Automatically applies an EDD discount code if certain cart conditions are met.
 * Version: 1.0
 * Author: Nose Graze
 * Author URI: https://www.nosegraze.com
 * License: GPL2
 * 
 * @package edd-auto-apply-discount-code
 * @copyright Copyright (c) 2016, Nose Graze Ltd.
 * @license GPL2+
 * 
 * INSTRUCTIONS:
 * 
 * This plugin isn't meant to be installed as-is. You'll need to comb through the code and
 * make changes for it to apply to your circumstances and requirements.
 * 
 * First create a discount code in EDD with no restrictions. We'll be adding the restrictions
 * manually in the code.
 * 
 * Then edit the discount name in the code to reflect your own.
 * 
 * Finally, you'll need to edit this logic to suit your needs.
 */

// Exit if accessed directly
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Maybe Apply 20% Discount
 *
 * Automatically applied if UBB is in the cart and at least one theme or paid add-on.
 *
 * @since 1.0
 * @return void
 */
function ng_edd_maybe_apply_discounts() {
	$cart_items       = edd_get_cart_contents();
	$discount_code    = 'UBB_Bonus'; // Change this to your custom discount code.
	$discount_applies = $has_ubb = $has_theme = $has_addons = false;

	if ( is_array( $cart_items ) ) {
		foreach ( $cart_items as $item ) {
			$post         = get_post( $item['id'] );
			$currentprice = get_post_meta( $post->ID, 'edd_price', true );

            		// This is the Ultimate Book Blogger plugin.
			if ( $item['id'] == 8779 ) {
				$has_ubb = true;
			}

            		// Product is a WordPress theme (in the "WordPress Themes" category).
			if ( has_term( 'WordPress Themes', 'download_category', $post ) ) {
				$has_theme = true;
			}

            		// Product is a UBB Add-On with a price greater than zero.
			if ( has_term( 'UBB Add-On', 'download_tag', $post ) && $currentprice > 0 ) {
				$has_addons = true;
			}
		}
	}

	// Has UBB and a theme.
	if ( $has_ubb && $has_theme ) {
		$discount_applies = true;
	}

	// Has UBB and one or more add-ons.
	if ( $has_ubb && $has_addons ) {
		$discount_applies = true;
	}

	if ( $discount_applies ) {
		edd_set_cart_discount( $discount_code );
	} else {
		edd_unset_cart_discount( $discount_code );
	}
}

add_action( 'edd_cart_items_before', 'ng_edd_maybe_apply_discounts' );