title: is_user_logged_in() not working in wordpress plugin
body: <p><code>is_user_logged_in()</code> function not working in WordPress plugin.
  Shows the following error:</p>
  <blockquote>
  <p>Fatal error: Call to undefined function <code>is_user_logged_in()</code> in
  How can I use the logic in WordPress plugin?</p>
  </blockquote>