Parse the side effect variable $http_response_header of file_get_contents().

http_parse_response_header.php

<?php

/**
 * http_parse_response_header()
 *   Parse $http_response_header produced by file_get_contents().
 *
 * @param array $header
 *   Supposed $http_response_header or array alike.
 * @param array
 *   Assoc array of the parsed version.
 */
function http_parse_response_header($header) {
  if (empty($header)) return []; // return empty array

  // parse status line
  $status_line = array_shift($header);
  if (!preg_match('/^(\w+)\/(\d+\.\d+) (\d+) (.+?)$/', $status_line, $matches))
    throw new Exception("misformat status line: {$status_line}");

  return [
    'PROTOCOL' => $matches[1],
    'PROTOCOL_VERSION' => $matches[2],
    'STATUS_CODE' => $matches[3],
    'STATUS' => $matches[4],
  ] + array_reduce($header, function ($carry, $line) {
    // parse content line
    list($key, $value) = explode(':', $line, 2);
    if (!isset($carry[$key])) {
      $carry[$key] = trim($value);
    } else {
      $carry[$key] .= "\n" . trim($value);
    }
    return $carry;
  }, []);
}

Example use:

<?php

$response = file_get_contents('https://foobar.com');
$response_header = http_parse_response_header($http_response_header);

if ($response_header['STATUS_CODE'] != '200') {
  echo "Error ({$response_header['STATUS_CODE']}): {$response_header['STATUS']}";
} else {
  echo $response;
}

?>