WordPress custom function display only parent terms

functions.php

function get_parent_terms_function($postid=null,$taxonomy){
  if ($postid === null)
  return false;

  $terms=wp_get_post_terms($postid,$taxonomy);

  if($terms){
    foreach ( $terms as $term ) {
        if($term->parent=='0') $termarr[]=$term;
    }
    return $termarr;
  }
  return false;
}

page.php

$terms = get_parent_terms_function( $post_id, 'your_custom_taxonomy' );
foreach ( $terms as $term ) {
  echo($term->name);
}