Need Woocommerce to only allow 1 product in the cart. If a product is already in the cart and another 1 is added then it should remove the previous 1

Question

I think this code should work but not exactly sure where to place it. Everywhere I have tried has failed so far...

add_action('init', 'woocommerce_clear_cart');  function woocommerce_clear_cart() { global $woocommerce, $post, $wpdb;  $url = explode('/', 'http://'.$_SERVER["HTTP_HOST"] . $_SERVER["REQUEST_URI"]); $slug=$url[4]; $postid = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE post_status='publish' AND post_name = '$slug'");      if ($postid){         if ($postid == PRODUCTID1 || $postid == PRODUCTID2){         $woocommerce->cart->empty_cart();         }     }  } 

Answer 1

Unfortunately there is no 'action' hook before WooCommerce adds an item to the cart. But they have a 'filter' hook before adding to cart. That is how I use it:

add_filter( 'woocommerce_add_cart_item_data', 'woo_custom_add_to_cart' );  function woo_custom_add_to_cart( $cart_item_data ) {      global $woocommerce;     $woocommerce->cart->empty_cart();      // Do nothing with the data and return     return $cart_item_data; }