in_array() not passing in function

//Auto add and update Title field:
  function my_post_title_updater( $post_id ) {

    $my_post = array();
    $my_post['ID'] = $post_id;
    $posttypes = array( 'page', 'post', 'portfolio' );
    $currentposttype = get_post_type();

    if ( in_array( $currentposttype, $posttypes ) ) {
      $my_post['post_title'] = get_field('kop');
    }

    //Unhook function to prevent infitnite looping
    remove_filter('acf/save_post', 'my_post_title_updater', 1);

    // Update the post into the database
    wp_update_post( $my_post );

    //Rehook function to prevent infitnite looping
    add_filter('acf/save_post', 'my_post_title_updater', 20, 3);

  }

  // run after ACF saves the $_POST['fields'] data
  add_action('acf/save_post', 'my_post_title_updater', 20);

if ( get_post_type() == 'page' ||  get_post_type() == 'post' || get_post_type() == 'portfolio') {
      $my_post['post_title'] = get_field('kop');
}