PHP gzip 压缩数据 html数据，减少网络流量

<?php
 ob_start("ob_gzhandler");
 ob_start("compress");
 header("Content-type: text/css; charset: UTF-8");
 header("Cache-Control: must-revalidate");
 $off = 0; # Set to a reaonable value later, say 3600 (1 hr);
 $exp = "Expires: " . gmdate("D, d M Y H:i:s", time() + $off) . " GMT";
 header($exp);
 
function compress($buffer) {
     $buffer = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $buffer); // remove comments
     $buffer = str_replace(array("\r\n", "\r", "\n", "\t", '  ', '    ', '    '), '', $buffer); // remove tabs, spaces, newlines, etc.
     $buffer = str_replace('{ ', '{', $buffer); // remove unnecessary spaces.
     $buffer = str_replace(' }', '}', $buffer);
     $buffer = str_replace('; ', ';', $buffer);
     $buffer = str_replace(', ', ',', $buffer);
     $buffer = str_replace(' {', '{', $buffer);
     $buffer = str_replace('} ', '}', $buffer);
     $buffer = str_replace(': ', ':', $buffer);
     $buffer = str_replace(' ,', ',', $buffer);
     $buffer = str_replace(' ;', ';', $buffer);
     return $buffer;
 }
 
require_once('screen.css');
 require_once('layout.css');
 require_once('custom.php');
 require_once('titles.css');
 require_once('bus.css');
 
?>