Block access to wp-admin

// Blocks access to /wp-admin/ for any user without the identified capability (edit_options=administrator)
add_action( 'init', 'my_block_admin_init' );
function my_block_admin_init() {
  if ( is_admin() && ! current_user_can( 'edit_options' ) && 
     ! ( defined( 'DOING_AJAX' ) && DOING_AJAX ) ) {
    wp_redirect( home_url() );
    exit;
  }
}