| 指令 | 含义 |
| public | 可以在任何地方缓存 |
| private | 只能被浏览器缓存 |
| no-cache | 不能在任何地方缓存 |
| must-revalidate | 缓存必须检查更新版本 |
| proxy-revalidate | 代理缓存必须检查更新版本 |
| max-age | 内容能够被缓存的时期，以秒表示 |
| s-maxage | 覆盖共享缓存的max-age设置 |
下面实例利用header（）设置浏览器的缓存：
<?php # Script 2.7 - view_tasks.php
// Connect to the database:
$dbc = @mysqli_connect (‘localhost‘, ‘username‘, ‘password‘, ‘test‘) OR die (‘<p>Could not connect to the database!</p></body></html>‘);
// Get the latest dates as timestamps:
$q = ‘SELECT UNIX_TIMESTAMP(MAX(date_added)), UNIX_TIMESTAMP(MAX(date_completed)) FROM tasks‘;
$r = mysqli_query($dbc, $q);
list($max_a, $max_c) = mysqli_fetch_array($r, MYSQLI_NUM);
// Determine the greater timestamp:
$max = ($max_a > $max_c) ? $max_a : $max_c;
// Create a cache interval in seconds:
$interval = 60 * 60 * 6; // 6 hours
// Send the header:
header ("Last-Modified: " . gmdate (‘r‘, $max));
header ("Expires: " . gmdate ("r", ($max + $interval)));
header ("Cache-Control: max-age=$interval");
?> <?php $interval=60*60*6 ; ?>
<?php
header("Last-Modified:".gmdate("r",($max+$interval)));
?><?php
header ("Expires: " . gmdate ("r", ($max + $interval)));
?><?php
header ("Cache-Control: max-age=$interval");
?>
getallheaders()函数：
<?php
foreach (getallheaders() as $name => $value) {
echo "$name: $value\n"."<br />";
}
?>输出结果：Host: 127.0.0.1 Connection: keep-alive Cache-Control: max-age=0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8 User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.76 Safari/537.36 Referer: http://127.0.0.1/liu/ Accept-Encoding: gzip,deflate,sdch Accept-Language: zh-CN,zh;q=0.8
原文：http://blog.csdn.net/phpfenghuo/article/details/18363939