客戶端緩存下載文件

Question

如何強制瀏覽器/客戶端緩​​存下載的文件？以下是我目前的腳本，如果HTTP_IF_MODIFIED_SINCE與文件具有相同的日期，則發送Last-Modified標題。問題是HTTP_IF_MODIFIED_SINCE從未設置，如下面的$_SERVER數據所示。

$filename="myFile.pdf"; 
$filetime=filemtime($filename); 
$array=array(); 
foreach($_SERVER as $key=>$value){syslog(LOG_INFO,$key.'=>'.print_r($value,1));} 
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && (@strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) == $filetime)) 
{ 
    syslog(LOG_INFO,'Send Cache headers'); 
    header('Last-Modified: '.gmdate('D, d M Y H:i:s', $filetime).' GMT', true, 304); 
} 
else 
{ 
    //Not yet cached 
    syslog(LOG_INFO,'download new file'); 
    $minutes=60*60*24*14; 
    header('Pragma: public'); 
    header('Cache-Control: public'); 
    header("Cache-Control: maxage=".$minutes); 
    header('Expires: ' . gmdate('D, d M Y H:i:s', time()+$minutes) . ' GMT'); 
    header('Last-Modified: '.gmdate('D, d M Y H:i:s', $filetime).' GMT', true, 200); 
    header('Content-Type: application/pdf'); 
    header('Content-Description: File Transfer'); 
    header('Content-Disposition: attachment; filename='.$filename.';'); 
    header('Content-Transfer-Encoding: binary'); 
    header('Content-Length: '.filesize($filename)); 
    @readfile($filename); 
} 

$ _ SERVER

Jun 2 16:41:13 localhost httpd: HTTP_HOST=>example.com 
Jun 2 16:41:13 localhost httpd: HTTP_USER_AGENT=>Mozilla/5.0 (Windows NT 6.1; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0 
Jun 2 16:41:13 localhost httpd: HTTP_ACCEPT=>text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 
Jun 2 16:41:13 localhost httpd: HTTP_ACCEPT_LANGUAGE=>en-US,en;q=0.5 
Jun 2 16:41:13 localhost httpd: HTTP_ACCEPT_ENCODING=>gzip, deflate 
Jun 2 16:41:13 localhost httpd: HTTP_CONNECTION=>keep-alive 
Jun 2 16:41:13 localhost httpd: PATH=>/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin 
Jun 2 16:41:13 localhost httpd: SERVER_SIGNATURE=><address>Apache/2.2.3 (CentOS) Server at example.com Port 80</address> 
Jun 2 16:41:13 localhost httpd: SERVER_SOFTWARE=>Apache/2.2.3 (CentOS) 
Jun 2 16:41:13 localhost httpd: SERVER_NAME=>example.com 
Jun 2 16:41:13 localhost httpd: SERVER_ADDR=>192.168.0.103 
Jun 2 16:41:13 localhost httpd: SERVER_PORT=>80 
Jun 2 16:41:13 localhost httpd: REMOTE_ADDR=>000.000.000.000 
Jun 2 16:41:13 localhost httpd: DOCUMENT_ROOT=>/var/www/html 
Jun 2 16:41:13 localhost httpd: SERVER_ADMIN=>root@localhost 
Jun 2 16:41:13 localhost httpd: SCRIPT_FILENAME=>/var/www/html/testing/download/index.php 
Jun 2 16:41:13 localhost httpd: REMOTE_PORT=>00000 
Jun 2 16:41:13 localhost httpd: GATEWAY_INTERFACE=>CGI/1.1 
Jun 2 16:41:13 localhost httpd: SERVER_PROTOCOL=>HTTP/1.1 
Jun 2 16:41:13 localhost httpd: REQUEST_METHOD=>GET 
Jun 2 16:41:13 localhost httpd: QUERY_STRING=> 
Jun 2 16:41:13 localhost httpd: REQUEST_URI=>/testing/download/ 
Jun 2 16:41:13 localhost httpd: SCRIPT_NAME=>/testing/download/index.php 
Jun 2 16:41:13 localhost httpd: PHP_SELF=>/testing/download/index.php 
Jun 2 16:41:13 localhost httpd: REQUEST_TIME=>1370216473 

Answer 1

你不能強迫緩存或它的發生計數。甚至沒有要求瀏覽器具有緩存功能。