Prepare cart with products

functions.php

<?php

class studiowp_add_products_to_cart {

	private $products = array();
	private $id = '';

	public function __construct( $id = 1, $products = array() ) {
		$this->products = $products;
		$this->id = $id;
		add_action( 'init', array( $this, 'init' ) );
	}

	public function init() {
		if ( isset( $_GET['studiowp_add_to_cart'] ) && $_GET['studiowp_add_to_cart'] == $this->id ) {
			$cart = WC()->cart;
			$cart->empty_cart();
			foreach ( $this->products as $product_id ) {
				$cart->add_to_cart( $product_id, 1 );
			}
			wp_safe_redirect( wc_get_cart_url() );
			exit;
		}
	}

}

new studiowp_add_products_to_cart(
	$id = 'my_products',
	$products = array( 35, 31, 31 )
);