CURL and HTTPS, "Cannot resolve host"


Question

I'm trying to fetch the contents of a page using CURL. The page that is doing the fetching is https and the page it is trying to fetch is also https. I'm getting an error "Couldn't resolve host" with all of the settings I try.

$c=curl_init();
curl_setopt($c, CURLOPT_URL,$url);
//curl_setopt($c, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:x.x.x) Gecko/20041107 Firefox/x.x");
curl_setopt ($c, CURLOPT_RETURNTRANSFER, TRUE);
//curl_setopt($c, CURLOPT_SSL_VERIFYPEER, TRUE);
//curl_setopt($c, CURLOPT_SSL_VERIFYHOST, TRUE);
curl_setopt($c, CURLOPT_HEADER, FALSE);

$html=curl_exec($c);

if($html === false) {
    echo curl_error($c);
}
else {
    echo 'Operation completed without any errors';
}   


curl_close($c);

Any ideas?

1
35
8/27/2009 2:57:12 PM

Accepted Answer

Maybe a DNS issue?

Try your URL against this code:

$_h = curl_init();
curl_setopt($_h, CURLOPT_HEADER, 1);
curl_setopt($_h, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($_h, CURLOPT_HTTPGET, 1);
curl_setopt($_h, CURLOPT_URL, 'YOUR_URL' );
curl_setopt($_h, CURLOPT_DNS_USE_GLOBAL_CACHE, false );
curl_setopt($_h, CURLOPT_DNS_CACHE_TIMEOUT, 2 );

var_dump(curl_exec($_h));
var_dump(curl_getinfo($_h));
var_dump(curl_error($_h)); 
25
2/1/2016 8:05:42 PM

I found that CURL can decide to use IPv6, in which case it tries to resolve but doesn't get an IPv6 answer (or something to that effect) and times out.

You can try the command line switch -4 to test this out.

In PHP, you can configure this line by setting this:

curl_setopt($_h, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4 );

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