Php中的瀏覽器緩存控制系統

Question

我試圖構建一個用PHP編寫的瀏覽器緩存控制系統。

在深多了，我想服務用PHP每一個瀏覽器請求，以產生正確的HTTP響應頭的以產生HTTP 200或HTTP 304未修改在合適的時間。

最大的問題是：我如何委派PHP來檢查資源是HTTP 200還是HTTP 304？

Answer 1

下面是一些示例代碼，用於管理PHP提供頁面的瀏覽器緩存。您需要確定一個時間戳$myContentTimestamp，指出頁面上內容的上次​​修改時間。

// put this line above session_start() to disable PHP's default behaviour of disabling caching if you're using sessions 
session_cache_limiter(''); 

$myContentTimestamp = 123456789; // here, get the last modified time of the content on this page, ex. a DB record or file modification timestamp 

// browser will send $_SERVER['HTTP_IF_MODIFIED_SINCE'] if it has a cache of your page 
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) >= $myContentTimestamp) { 
    // browser's cache is the latest version, so tell the browser there is no newer content and exit 
    header('HTTP/1.1 304 Not Modified'); 
    header('Last-Modified: ' . date("D M j G:i:s T Y", $myContentTimestamp)); 
    die; 
} else { 
    // tell the browser the last change date of this page's content 
    header('Last-Modified: ' . date("D M j G:i:s T Y", $myContentTimestamp)); 
    // tell the browser it has to ask if there are any changes whenever it shows this page 
    header("Cache-Control: must-revalidate"); 

    // now show your page 
    echo "hello world! This page was last modified on " . date('r', $myContentTimestamp); 
}