title: Save input field contact form 7 to post meta
body: <p>I want to calculate the inventory down to zero via storing the input of a number field.</p>
  <p>So far i have the following:</p>
  <pre><code>add_action( 'wpcf7_before_send_mail',
      function( $contact_form, $abort, $submission ) {
         $post_id = get_the_id();
         $voorraad = '';
         if ($post_id === 5080){
         $voorraad = get_post_meta(5080,'voorraad',true);
         $newvoorraad = implode( ', ', (array) $submission-&gt;get_posted_data( 'number-435' ));
         $stock = $voorraad - $newvoorraad;
         update_post_meta($post_id, 'voorraad', $stock);
           }
      },10,3
      );
  </code></pre>
  <p>However, this does not work.</p>
  <p>The meta field voorraad exists and has value 450. However, the field is not updated after input. I cannot store the submitted data in the first place, even if i use an empty meta field with a different name and store a set string like 'example', only for testing purposes.</p>
  <p>How can i store a user input in a meta field upon submission?</p>
  <p>Any ideas?</p>