Had same problem - it was somewhere in the ca certificate, so I used the ca bundle used for curl, and it worked. You can download the curl ca bundle here: https://curl.haxx.se/docs/caextract.html
For encryption and security issues see this helpful article:
https://www.venditan.com/labs/2014/06/26/ssl-and-php-streams-part-1-you-are-doing-it-wrongtm/432
Here is the example:
$url = 'https://www.example.com/api/list';
$cn_match = 'www.example.com';
$data = array (
'apikey' => '[example api key here]',
'limit' => intval($limit),
'offset' => intval($offset)
);
// use key 'http' even if you send the request to https://...
$options = array(
'http' => array(
'header' => "Content-type: application/x-www-form-urlencoded\r\n",
'method' => 'POST',
'content' => http_build_query($data)
)
, 'ssl' => array(
'verify_peer' => true,
'cafile' => [path to file] . "cacert.pem",
'ciphers' => 'HIGH:TLSv1.2:TLSv1.1:TLSv1.0:!SSLv3:!SSLv2',
'CN_match' => $cn_match,
'disable_compression' => true,
)
);
$context = stream_context_create($options);
$response = file_get_contents($url, false, $context);
Hope that helps