PHP - Download file and preserve timestamp?

问题:

As the name suggests, is there a quick way to download a file, but bring the timestamp along?

I'm writing a basic cache that, among other checks, determines (via get_headers) if a given local file is the same as it's remote counterpart.

I know I can file_get_contents / file_put_contents and then touch() the file with the results of get_headers, but the calling that is making another HTTP call (even if it is a HEAD call) and I'd only like to test Last-Modified as a last resort.

So is there a quick, "one HTTP call" way to download a file and preserve the timestamp? Some remote files live on an FTP server, but many are text files, and / or live on a web server.

EDIT: Someone suggested a related question, but my question differs, in that I'm looking to get the remote modified date without having to make a second call, which the copy() based answer suggests

$http_response_header seems to do the trick, as suggested below.

回答1:

You can get cached Last-Modified from $http_response_header and use it to touch the file.

To automate it completely is obviously not possible as the stream cannot know where are you going to store it.

回答2:

You can use filemtime() to get last modified date and then touch() for modifying last modified date/time

Source: PHP copy file without changing the last modified date

回答3:

if (file_exists($cache_file) && (filemtime($cache_file) > (time() - 60 * 5 ))) {
   // Cache file is less than five minutes old. 
   // Don't bother refreshing, just use the file as-is.
   $file = file_get_contents($cache_file);
} else {
   // Our cache is out-of-date, so load the data from our remote server,
   // and also save it over our cache for next time.
   $file = file_get_contents($url);
   file_put_contents($cache_file, $file, LOCK_EX);
}