You can use CURLOPT_HEADERFUNCTION  with a callback inside an object.  This makes is it easy to capture the headers for later use.  For example:

<?php
class Test
{
    public $headers;

    //...

    public function exec($opts)
    {
        $this->headers = array();
        $opts[CURLOPT_HEADERFUNCTION] = array($this, '_setHeader');
        $ch = curl_init();
        curl_setopt_array($ch, $opts);
        return curl_exec($ch);
    }

    private function _setHeader($ch, $header)
    {
        $this->headers[] = $header;
        return strlen($header);
    }

    
}

$test = new Test();
$opts = array(
   //... your curl opts here
);
$data = $test->exec($opts);
print_r($test->headers);
?>

...something like that

(This works in php v. 5.1.4)