title: How to open a popup after the contact form 7 succesfully submitted
body: <p>I am using Wordpress and Contact form 7. 
  I need to show a popup using magnificPopup js which will come after the successfully submission of the contact form.
  Have added an hook for the wpcf7_mail_sent, but how can I call popup to show using javascript.</p>
  
  <p>Example :</p>
  
  <p><strong>In functions.php</strong></p>
  
  <pre><code>add_action( 'wpcf7_mail_sent', 'after_send_mail_from_contact_form' );
  function after_send_mail_from_contact_form($contact_form){
    // what to do here 
  }
  </code></pre>
  
  <p><strong>in Custom.js file</strong></p>
  
  <pre><code>$('.pay_for_course').magnificPopup({
     disableOn: 700,
     type: 'iframe',
     mainClass: 'mfp-fade',
     removalDelay: 160,
     preloader: false,
     fixedContentPos: false
  });
  </code></pre>