Code-Snippets-Functions/Execute a function on a child site/Easy Digital Downloads/prevent-duplicate-cart-items.txt

function pw_edd_prevent_duplicate_cart_items( $download_id, $options ) {
	if( edd_item_in_cart( $download_id, $options ) ) {
		if( edd_is_ajax_enabled() && defined('DOING_AJAX') && DOING_AJAX ) {
			die('1');
		} else {
			wp_redirect( edd_get_checkout_uri() ); exit;
		}
	}
}
add_action( 'edd_pre_add_to_cart', 'pw_edd_prevent_duplicate_cart_items', 10, 2 );