title: Change Woocommerce email subject if order have this specific category
body: <p>I just want to know if possible to change the email subject if the order have the specific category like (Preorder). I want to put PO at beginning (PO New customer order #0000) then all other order the customer receive the default email subject (New Customer Order #0000).</p>
  
  <pre><code>add_filter('woocommerce_email_subject_new_order', 'change_admin_email_subject', 1, 2);
  function change_admin_email_subject( $subject, $order ) {
  
      global $woocommerce;
      global $product;       
      if ( has_term( 'preorder', $product-&gt;ID ) ) {           
          $blogname = wp_specialchars_decode(get_option('blogname'), ENT_QUOTES);
          $subject = sprintf( '[%s]New customer order (# %s) from %s %s', $blogname, $order-&gt;id, $order-&gt;billing_first_name, $order-&gt;billing_last_name );
      } 
      return $subject;
  }
  </code></pre>
  
  <p>Note: I just copy this code somewhere.</p>