Automatically add product to cart on visit

wc-auto-add-product-to-cart.php

/**
 * Automatically add product to cart on visit
 */
add_action( 'template_redirect', 'add_product_to_cart' );
function add_product_to_cart() {
	if ( ! is_admin() ) {
		$product_id = 64; //replace with your own product id
		$found = false;
		//check if product already in cart
		if ( sizeof( WC()->cart->get_cart() ) > 0 ) {
			foreach ( WC()->cart->get_cart() as $cart_item_key => $values ) {
				$_product = $values['data'];
				if ( $_product->get_id() == $product_id )
					$found = true;
			}
			// if product not found, add it
			if ( ! $found )
				WC()->cart->add_to_cart( $product_id );
		} else {
			// if no products in cart, add it
			WC()->cart->add_to_cart( $product_id );
		}
	}
}

Thanks, @bdthemes! Updated!

I want to offer option to remove the product from cart, if the customer doesn't want it. How can I do that?

In my store I would like to automatically add a certain product depending on the category of the product that the user adds. How would it be?

Thank you for the script.

I try it on my website, but it triggers an error to the website. Following is the error message.

An error of type E_ERROR was caused in line 13 of the file /nas/content/live/acewasteprod/wp-content/plugins/code-snippets/php/snippet-ops.php(446) : eval()'d code. Error message: Uncaught Error: Call to a member function get_cart() on null in /nas/content/live/acewasteprod/wp-content/plugins/code-snippets/php/snippet-ops.php(446) : eval()'d code:13

Does anyone know how to resolve this issue?

Thank you in advance.

Very useful.

It's not possible to remove the item from the cart with this script as it runs more than once.
Maybe have a counter value stored in a meta field or would there be a better way?

Many thanks.

I want to offer option to remove the product from cart, if the customer doesn't want it. How can I do that?

try this because it only adds the product if the cart is empty:
/**

• Automatically add product to cart on visit
  */
  add_action( 'template_redirect', 'add_product_to_cart' );
  function add_product_to_cart()
  {
  // check if cart contents are empty
  if ( WC()->cart->get_cart_contents_count() == 0 )
  {
  // this code only runs the first time the hook is fired
  if ( ! is_admin() )
  {
  $product_id = 2765; //replace with your own product id
  WC()->cart->add_to_cart( $product_id );
  }
  }
  }