file_get_contents receive cookies

There’s a magic variable for this, called $http_response_header; it’s an array comprising all headers that were received. To extract the cookies you have to filter out the headers that start with Set-Cookie:.

file_get_contents('http://example.org');

$cookies = array();
foreach ($http_response_header as $hdr) {
    if (preg_match('/^Set-Cookie:\s*([^;]+)/', $hdr, $matches)) {
        parse_str($matches[1], $tmp);
        $cookies += $tmp;
    }
}
print_r($cookies);

An equivalent but less magical approach would be to use stream_get_meta_data():

if (false !== ($f = fopen('http://www.example.org', 'r'))) {
        $meta = stream_get_meta_data($f);
        $headers = $meta['wrapper_data'];

        $contents = stream_get_contents($f);
        fclose($f);
}
// $headers now contains the same array as $http_response_header