Search code examples
phpcachingheaderetag

How to use etags in a PHP file?

How do you implemented etags inside a PHP file? What do I upload to the server and what do I insert into my PHP file?

Solution

  • Create / edit your .htaccess file and add the following:

    FileETag MTime Size

    Either place the following inside a function or put it at the top of the PHP file that you need etags to work on:

    <?php 
    $file = 'myfile.php';
    $last_modified_time = filemtime($file); 
    $etag = md5_file($file); 

    header("Last-Modified: ".gmdate("D, d M Y H:i:s", $last_modified_time)." GMT"); 
    header("Etag: $etag"); 

    if (@strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) == $last_modified_time || 
        trim($_SERVER['HTTP_IF_NONE_MATCH']) == $etag) { 
        header("HTTP/1.1 304 Not Modified"); 
    exit; 
} 
?>