/************* Display the page or post slug *****************/ Just use get_slug() Use this in Functions.php

get_slug()

/************* Display the page or post slug *****************/
function get_the_slug( $id=null ){
  if( empty($id) ):
    global $post;
    if( empty($post) )
      return ''; // No global $post var available.
    $id = $post->ID;
  endif;

  $slug = basename( get_permalink($id) );
  return $slug;
}

function the_slug( $id=null ){
  echo apply_filters( 'the_slug', get_the_slug($id) );
}