是否可以仅发送http请求以获取上次修改时间？

Question

Instead of the file itself?

EDIT

Best with a demo in PHP?

Answer 1

Yes. The "HEAD" method returns only the response headers and not the actual data.

Answer 2

You can use php's get_headers function

$a = get_headers('http://sstatic.net/so/img/logo.png');
print_r($a);

Answer 3

In your HTTP request you should add any of these header attributes, and you may receive an 304 (Last modified)

1. If-Modified-Since
2. If-None-Match
3. If-Unmodified-Since

Andrei is correct, HEAD will only get the headers. My suggestion will return only the header and no body if the condictions are met. If the content has been updated the body will contain the new information.

Answer 4

<?php
// Get Headers
$ch = curl_init(); 
curl_setopt($ch, CURLOPT_URL,            'http://example.com/'); 
curl_setopt($ch, CURLOPT_HEADER,         true); 
curl_setopt($ch, CURLOPT_NOBODY,         true); 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); 
curl_setopt($ch, CURLOPT_TIMEOUT,        10); 
$response = curl_exec($ch); 

// Process Headers
$headerLines = explode("\r\n", $response);
foreach ($headerLines as $headerLine) {
    $headerLineParts = explode(': ', $headerLine);
    if (count($headerLineParts) >= 2) {
        $headers[$headerLineParts[0]] = $headerLineParts[1];
    }
}

echo $headers['Last-Modified'];
?>

Answer 5

您需要编写一些服务来处理http请求，并提取所请求文件的最后修改日期，然后返回该日期作为响应。