title: How to get the Variation ID in a Woocommerce product
body: <p>I'm trying to get in a plugin I'm writing the variation ID of products. Here's what I wrote:</p>
  
  <pre><code>class mass {
  
      public function __construct()
      {
          add_action('woocommerce_product_after_variable_attributes',array($this,'thfo_mass'));
  
  
      }
  public function thfo_mass()
      {
          $id = WC_Product_Variation::get_variation_id();
          //$lenght = get_post_meta($id,'_length');
          //$dimensions = wc_get_dimension(24750, 'cm');
          var_dump($id);
      }
  </code></pre>
  
  <p>I only get an error:</p>
  
  <blockquote>
    <p>Deprecated: Non-static method WC_Product_Variation::get_variation_id() should not be called statically, assuming $this from incompatible context in path/to/plugins/thfo-raw-material-for-woocommerce/class/mass.php on line 19</p>
    
    <p>Notice: Undefined property: mass::$variation_id in path/to/wp-content/plugins/woocommerce/includes/class-wc-product-variation.php on line 257
    int(0) </p>
  </blockquote>