Compress HTML output with CodeIgniter

compress.php

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');
 
function compress()
{
  $CI =& get_instance();
  $buffer = $CI->output->get_output();

  $search = array(
    '/\>[^\S ]+/s', 
    '/[^\S ]+\</s', 
     '/(\s)+/s', // shorten multiple whitespace sequences
  '#(?://)?<!\[CDATA\[(.*?)(?://)?\]\]>#s' //leave CDATA alone
  );
  $replace = array(
     '>',
     '<',
     '\\1',
  "//&lt;![CDATA[\n".'\1'."\n//]]>"
  );

  $buffer = preg_replace($search, $replace, $buffer);

  $CI->output->set_output($buffer);
  $CI->output->_display();
}
 
/* End of file compress.php */
/* Location: ./system/application/hooks/compress.php */

//------system/application/hooks/compress.php
?>

config.php

<?php
//------system/application/config/config.php

$config['enable_hooks'] = TRUE;

?>

hooks.php

<?php
//------system/application/config/hooks.php
// compress output
$hook['display_override'][] = array(
  'class' => '',
  'function' => 'compress',
  'filename' => 'compress.php',
  'filepath' => 'hooks'
);
?>

how can i use this?