gistfile1.php

<?php
// $input is a string. return value is a hash.
function parse_input($input) {
  $url = @parse_url($input);
  if (!$url) {
    die("That isn't a valid identifier!\n");
  }
  if (isset($url['user']) || isset($url['pass'])) {
    die("We don't support username:password syntax.\n");
  }
  if (isset($url['fragment'])) {
    die("We don't support URL fragments.\n");
  }
  if (isset($url['query'])) {
    die("Query parameters in OpenIDs are a bad idea!\n");
  }

  $identifier = array(
    'scheme' => NULL,
    'user'   => NULL,
    'domain' => NULL,
    'port'   => NULL,
    'path'   => NULL,
  );

  // email?
  if (isset($url['path']) && strpos($url['path'], '@') !== false) {
    list($user, $domain) = explode('@', $url['path']);

    $identifier['scheme'] = 'acct';
    $identifier['user']   = $user;
    $identifier['domain'] = $domain;

  } else { // some form of URL
    if (isset($url['host'])) {
      $identifier['scheme'] = strtolower($url['scheme']);
      $identifier['domain'] = $url['host'];
      $identifier['port'] = isset($url['port']) ? $url['port'] : NULL;
      $identifier['path'] = isset($url['path']) ? $url['path'] : NULL;

    } elseif (isset($url['path'])) { // user didn't include a scheme
      if (strpos($url['path'], '/') !== false) {
        list($domain, $path) = explode('/', $url['path']);
      } else {
        $domain = $url['path'];
        $path = NULL;
      }

      $identifier['scheme'] = 'http';
      $identifier['domain'] = $domain;
      $identifier['port'] = isset($url['port']) ? $url['port'] : NULL;
      $identifier['path'] = $path ? '/' . $path : NULL;
    }
  }

  // make sure we got something
  if (!$identifier['domain']) {
    die("Not sure what you gave us: $input\n");
  }

  // make sure we ended up with a valid scheme
  if (!in_array($identifier['scheme'], array('http', 'https', 'acct'))) {
    die("Invalid URI scheme\n");
  }

  return $identifier;
}