title: How to check if WooCommerce plugin is enabled?
body: <p>I'm trying to check if woo commerce plugin is active then add some options to the option panel. but this code doesn't work right.</p>
  <p>can anyone tell me what is wrong?
  thanks.</p>
  <pre><code> if( class_exists( 'WooCommerce' )) {//add options}
  </code></pre>