php - How to add filter or hook for "woocommerce_add_to_cart"

Question

I want add to cart two product at the same time, one is original (current) product and second is from drop-down list

add_action('woocommerce_add_to_cart', 'custome_add_to_cart');
$cnt=2
function custome_add_to_cart() {
    global $woocommerce;
      $cnt = $cnt + 1;
      echo $cnt."X";
      echo $p_id=$_POST['assessories'];
    $woocommerce->cart->add_to_cart($p_id, 1);

}

Output:- As you can see in output image below , it adding same drop-down item many time in cart but i want only 1 quantity to add to cart. it seems that add_to_cart function run many times. What should i do or how to add filter with passing second drop-down product as parameter to add to cart function ? so i can add this product also in cart.

Answer 1

This should work:

add_action('woocommerce_add_to_cart', 'custome_add_to_cart');
function custome_add_to_cart() {
    global $woocommerce;

    $product_id = $_POST['assessories'];

    $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->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 );
    }
}

Based on following source: https://docs.woothemes.com/document/automatically-add-product-to-cart-on-visit/