Prevent Subscribers from accessing wp-admin

no-subscribers-in-admin.php

<?php

// If users have multiple roles, refactor line 7 to check for required
// roles instead of rejecting Subscribers

add_action( 'init', function () { 
  if ( is_admin() 
  && in_array( 'subscriber', (array) $user->roles ) 
  && ! ( defined( 'DOING_AJAX' ) && DOING_AJAX ) 
  ) { wp_redirect( '/' ); exit; } 
});