gistfile1.txt

<?php

$ch = curl_init("https://opensky.com/api/v1/json/heartbeat");
curl_setopt($ch, CURLOPT_HEADER, TRUE); 
curl_setopt($ch, CURLOPT_NOBODY, TRUE);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);

curl_setopt($ch, CURLOPT_HTTPHEADER, array('X_OPENSKY_API_KEY: foobar')); 

$head = curl_exec($ch); 
$httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE); 
curl_close($ch);

print_r($head);
print_r("<hr />");
print_r($httpCode);