function wp_link_pages( $args = '' ) {
  global $page, $numpages, $multipage, $more;

  $defaults = array(
    'before'           => '<p class="post-nav-links">' . __( 'Pages:' ),
    'after'            => '</p>',
    'link_before'      => '',
    'link_after'       => '',
    'aria_current'     => 'page',
    'next_or_number'   => 'number',
    'separator'        => ' ',
    'nextpagelink'     => __( 'Next page' ),
    'previouspagelink' => __( 'Previous page' ),
    'pagelink'         => '%',
    'echo'             => 1,
  );

  $parsed_args = wp_parse_args( $args, $defaults );

  
/**
 * Filters the arguments used in retrieving page links for paginated posts.
 *
 * @since 3.0.0
 *
 * @param array $parsed_args An array of arguments for page links for paginated posts.
 */
  $parsed_args = apply_filters( 'wp_link_pages_args', $parsed_args );

  $output = '';
  if ( $multipage ) {
    if ( 'number' == $parsed_args['next_or_number'] ) {
      $output .= $parsed_args['before'];
      for ( $i = 1; $i <= $numpages; $i++ ) {
        $link = $parsed_args['link_before'] . str_replace( '%', $i, $parsed_args['pagelink'] ) . $parsed_args['link_after'];
        if ( $i != $page || ! $more && 1 == $page ) {
          $link = _wp_link_page( $i ) . $link . '</a>';
        } elseif ( $i === $page ) {
          $link = '<span class="post-page-numbers current" aria-current="' . esc_attr( $parsed_args['aria_current'] ) . '">' . $link . '</span>';
        }
        
/**
 * Filters the HTML output of individual page number links.
 *
 * @since 3.6.0
 *
 * @param string $link The page number HTML output.
 * @param int    $i    Page number for paginated posts' page links.
 */
        $link = apply_filters( 'wp_link_pages_link', $link, $i );

        // Use the custom links separator beginning with the second link.
        $output .= ( 1 === $i ) ? ' ' : $parsed_args['separator'];
        $output .= $link;
      }
      $output .= $parsed_args['after'];
    } elseif ( $more ) {
      $output .= $parsed_args['before'];
      $prev    = $page - 1;
      if ( $prev > 0 ) {
        $link = _wp_link_page( $prev ) . $parsed_args['link_before'] . $parsed_args['previouspagelink'] . $parsed_args['link_after'] . '</a>';

        
/** This filter is documented in wp-includes/post-template.php */
        $output .= apply_filters( 'wp_link_pages_link', $link, $prev );
      }
      $next = $page + 1;
      if ( $next <= $numpages ) {
        if ( $prev ) {
          $output .= $parsed_args['separator'];
        }
        $link = _wp_link_page( $next ) . $parsed_args['link_before'] . $parsed_args['nextpagelink'] . $parsed_args['link_after'] . '</a>';

        
/** This filter is documented in wp-includes/post-template.php */
        $output .= apply_filters( 'wp_link_pages_link', $link, $next );
      }
      $output .= $parsed_args['after'];
    }
  }

  
/**
 * Filters the HTML output of page links for paginated posts.
 *
 * @since 3.6.0
 *
 * @param string $output HTML output of paginated posts' page links.
 * @param array  $args   An array of arguments.
 */
  $html = apply_filters( 'wp_link_pages', $output, $args );

  if ( $parsed_args['echo'] ) {
    echo $html;
  }
  return $html;
}