WooCommerce URL to add to cart and redirect to cart or checkout with quantity, limit, and option to remove other products.

woocommerce-add-to-cart-url-with-redirect.php

<?php
/*
 * Returns a URL that upon visiting, will add the product to the cart and do some other things as described below.
 *   $qty = How many items to add to the cart
 *   $limit = If true, it will prevent you from having more than $qty in your cart.
 *   $remove_others = If true, any other products will be removed from the cart.
 *   $redirect_to = If set to "cart" or "checkout", will redirect after adding the item. Does not work with a URL (to avoid XSS).
 *
 * @param $product_id
 * @param int $qty
 * @param bool $limit
 * @param bool $remove_others
 * @param string $redirect_to
 *
 * @return string
 */
function woo_add_to_cart_url( $product_id, $qty = 1, $limit = false, $remove_others = false, $redirect_to = '' ) {
	$args = array(
	    'acrc' => wp_create_nonce( 'add_cart_redirect_checkout' ),
	    'acrc_id' => (int) $product_id,
	    'acrc_qty' => (int) $qty,
	    'acrc_limit' => $limit ? 1 : 0,
	    'acrc_remove_others' => $remove_others ? 1 : 0,
	    'acrc_redirect_to' => strtolower( (string) $redirect_to ),
	);

	return add_query_arg( $args, get_permalink() );
}

/**
 * Hook that implements ?add_to_cart_redirect property. This adds a product to the cart, and redirects to checkout.
 */
function woo_add_to_cart_redirect_checkout() {
	$nonce = isset($_REQUEST['acrc']) ? stripslashes($_REQUEST['acrc']) : false;
	if ( !$nonce || !wp_verify_nonce( $nonce, 'add_cart_redirect_checkout' ) ) return;

	$id = isset($_REQUEST['acrc_id']) ? (int) $_REQUEST['acrc_id'] : false;
	$qty = isset($_REQUEST['acrc_qty']) ? max( 1, (int) $_REQUEST['acrc_qty'] ) : false;
	$limit = isset($_REQUEST['acrc_limit']) ? (int) $_REQUEST['acrc_limit'] : false;
	$remove_others = isset($_REQUEST['acrc_remove_others']) ? (int) $_REQUEST['acrc_remove_others'] : false;
	$redirect_to = isset($_REQUEST['acrc_redirect_to']) ? stripslashes($_REQUEST['acrc_redirect_to']) : false;
	$skip_add_to_cart = false;

	// Remove any other product from the cart
	if ( $remove_others ) {
		foreach ( WC()->cart->get_cart() as $cart_item_key => $values ) {
			if ( $values['product_id'] !== $id ) WC()->cart->remove_cart_item( $cart_item_key );
		}
	}

	// Set the quantity if it is already in the cart.
	if ( $limit ) {
		foreach ( WC()->cart->get_cart() as $cart_item_key => $values ) {
			if ( $values['product_id'] == $id ) {
				WC()->cart->set_quantity( $cart_item_key, $qty );
				$skip_add_to_cart = true;
			}
		}
	}

	// Add to cart, unless we set quantity above instead
	if ( !$skip_add_to_cart ) {
		WC()->cart->add_to_cart( $id, $qty );
	}

	// Redirect to clear post/get query vars.
	if ( strtolower($redirect_to) == 'cart' ) $url = wc_get_cart_url();
	else if ( strtolower($redirect_to) == 'checkout' ) $url = wc_get_checkout_url();
	else $url = remove_query_arg( array( 'acrc', 'acrc_id', 'acrc_qty', 'acrc_limit', 'acrc_remove_others', 'acrc_redirect_to' ) );

	wp_redirect( $url );
	exit;
}
add_action( 'template_redirect', 'woo_add_to_cart_redirect_checkout', 5 );