<?php 
$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();