Fixes an issue with WooCommerce Tickets 3.9.1 and adding multiple items to the cart

temp-fix-wt391.php

<?php
/**
 * Moves the add-to-cart functionality to a later point in the request (ie,
 * after the existing cart contents have been populated).
 */
function wootix_rehook_add_to_cart() {
	$wootickets = TribeWooTickets::get_instance();
	$callback = array( $wootickets, 'process_front_end_tickets_form' );

	// Switch to a later action
	remove_action( 'wp_loaded', $callback );
	add_action( 'wp_loaded', $callback, 50 );
}

// Apply fix if this snippet is running within a (mu-)plugin file
if ( ! did_action( 'plugins_loaded' ) ) {
	add_action( 'plugins_loaded', 'wootix_rehook_add_to_cart', 50 );
}
// Also apply fix if this snippet is embedded directly in a theme functions.php file
elseif ( class_exists( 'TribeWooTickets' ) ) {
	wootix_rehook_add_to_cart();
}