title: Woocommerce Add to Cart Condition
body: <p>I recently implement the code in function.php to redirect url when the price is 0 but it seems its only lacking and the price condition is not working. See my codes.</p>
  
  <pre><code>/**
   * Set a custom add to cart URL to redirect to
   * @return string
   **/
  
  function custom_add_to_cart_redirect() { 
        $_product = wc_get_product( $product_id );
        if( $product-&gt;get_price() == 0 ||  $product-&gt;get_price() == '') {
          return 'http://www.nichegas.ads-tracker.com/contact/'; 
          }
  }
  add_filter( 'woocommerce_add_to_cart_redirect', 'custom_add_to_cart_redirect' );
  </code></pre>
  
  <p>It seems I am lacking on some code or something. 
  Our objective are:
   1. IF price is 0 it will redirect to out custom url
   2  also when click the add to card and its zero its will not add the item to the cart. How to disable the addition of product?</p>
  
  <p>Your help will very much appreciated. Have a nice day!</p>