How to get info on sent PHP curl request

If you set CURLINFO_HEADER_OUT to true, outgoing headers are available in the array returned by curl_getinfo(), under request_header key:

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "http://foo.com/bar");
curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
curl_setopt($ch, CURLOPT_USERPWD, "someusername:secretpassword");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLINFO_HEADER_OUT, true);

curl_exec($ch);

$info = curl_getinfo($ch);
print_r($info['request_header']);

This will print:

GET /bar HTTP/1.1
Authorization: Basic c29tZXVzZXJuYW1lOnNlY3JldHBhc3N3b3Jk
Host: foo.com
Accept: */*

Note the auth details are base64-encoded:

echo base64_decode('c29tZXVzZXJuYW1lOnNlY3JldHBhc3N3b3Jk');
// prints: someusername:secretpassword

Also note that username and password need to be percent-encoded to escape any URL reserved characters (/, ?, &, : and so on) they might contain:

curl_setopt($ch, CURLOPT_USERPWD, urlencode($username).':'.urlencode($password));

You can also use a proxy tool like Charles to capture the outgoing request headers, data, etc. by passing the proxy details through CURLOPT_PROXY to your curl_setopt_array method.

For example:

$proxy = '127.0.0.1:8888';
$opt = array (
    CURLOPT_URL => "http://www.example.com",
    CURLOPT_PROXY => $proxy,
    CURLOPT_POST => true,
    CURLOPT_VERBOSE => true,
    );

$ch = curl_init();
curl_setopt_array($ch, $opt);
curl_exec($ch);
curl_close($ch);