add_action('get_header', 'pt_html_minify_start');
function pt_html_minify_start()  {
    ob_start( 'pt_html_minyfy_finish' );
}
function pt_html_minyfy_finish( $html )  {
  $html = preg_replace('/<!--(?!s*(?:[if [^]]+]|!|>))(?:(?!-->).)*-->/s', '', $html);
  $html = str_replace(array("\r\n", "\r", "\n", "\t"), '', $html);
  while ( stristr($html, '  '))
     $html = str_replace('  ', ' ', $html);
 return $html;
}