Is there a way to tell curl to not use cache

Question

I am trying to find out file size of an url:

$url1 = \'www.google.com\';
$curl1 = curl_init();
curl_setopt($curl1, CURLOPT_URL, $url1); 
curl_setopt($curl1, CURL         


        

Answer 1

You can use CURLOPT_FRESH_CONNECT for this. From curl_setopt

CURLOPT_FRESH_CONNECT TRUE to force the use of a new connection instead of a cached one.

curl_setopt($curl1, CURLOPT_FRESH_CONNECT, TRUE);

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According to RFC 7234 - Hypertext Transfer Protocol (HTTP/1.1): Caching and 5.2. Cache-Control

The "Cache-Control" header field is used to specify directives for caches along the request/response chain.

5.2.1. Request Cache-Control Directives defines several directives to control the use of caches for a response. One of these is

5.2.1.4. no-cache

The "no-cache" request directive indicates that a cache MUST NOT use a stored response to satisfy the request without successful validation on the origin server.

So setting an appropriate header with

curl_setopt($curl1, CURLOPT_HTTPHEADER, array("Cache-Control: no-cache");

should ensure, that a valid and up to date response will be returned. I understand, that this may still result in a cached response, if the validation on the server allows to do so.

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However, 5.2.2.1. must-revalidate is a Response Cache-Control Directive given by a server together with the response to a request

[...] The must-revalidate directive ought to be used by servers if and only if failure to validate a request on the representation could result in incorrect operation, such as a silently unexecuted financial transaction.