link_rel_parser.php

<?php
namespace IndieWeb;

/* 
http_rels, head_http_rels by Tantek Çelik http://tantek.com/
license: http://creativecommons.org/publicdomain/zero/1.0/
depends on: get_absolute_uri in https://github.com/tantek/cassis/cassis.js
*/

/**
 * @param string $h  HTTP headers as a string
 * @param string $url optional base URL to resolve relative URLs
 * @return array $rels rel values as indices to arrays of URLs, empty array if no rels at all
 */
function http_rels($h, $url = '') {
  $h = preg_replace("/(\r\n|\r)/", "\n", $h);
  $h = explode("\n", preg_replace("/(\n)[ \t]+/", " ", $h));
  $rels = array();
  foreach ($h as $f) {
    if (!strncasecmp($f, 'X-Pingback: ', 12)) {
      // convert to a link header and have common code handle it
      $f = 'Link: <' . trim(substr($f, 12)) . '>; rel="pingback"';
    }
    if (!strncasecmp($f, 'Link: ', 6)) {
      $links = explode(', ', trim(substr($f, 6)));
      foreach ($links as $link) {
        $hrefandrel = explode('; ', $link);
        $href = trim($hrefandrel[0], '<>');
        $relarray = '';
        foreach ($hrefandrel as $p) {
          if (!strncmp($p, 'rel=', 4)) {
            $relarray = explode(' ', trim(substr($p, 4), '"\''));
            break;
          }
        }
        if ($relarray !== '') { // ignore Link: headers without rel
          foreach ($relarray as $rel) {
            $rel = strtolower(trim($rel));
            if ($rel != '') {
              if (!array_key_exists($rel, $rels)) {
                $rels[$rel] = array();
              }
              if ($url) { 
                $href = get_absolute_uri($href, $url); 
              }
              if (!in_array($href, $rels[$rel])) {
                $rels[$rel][] = $href;
              }
            }
          }
        }
      }
    }
  }
  return $rels;
}

/**
 * @param $url  URL to get HTTP HEAD Link (and effective/x-extended) rels
 * @return array  "status"=> HTTP status code, "type"=> HTTP Content-Type, "rels" array with http_rels return value. empty array if no rels
 */
function head_http_rels($url) {
  $c = curl_init();
  curl_setopt($c, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt($c, CURLOPT_URL, $url);
  curl_setopt($c, CURLOPT_CONNECTTIMEOUT, 2);
  curl_setopt($c, CURLOPT_TIMEOUT, 4);
  curl_setopt($c, CURLOPT_USERAGENT, 'head_http_rels function');
// curl_setopt($c, CURLOPT_FOLLOWLOCATION, 1);
// commented out due to:
// Warning: curl_setopt(): CURLOPT_FOLLOWLOCATION cannot be activated when an open_basedir is set
  curl_setopt($c, CURLOPT_SSL_VERIFYPEER , false );
  curl_setopt($c, CURLOPT_SSL_VERIFYHOST , false );
  curl_setopt($c, CURLOPT_HEADER, true);
  curl_setopt($c, CURLOPT_NOBODY, true);
  $h = curl_exec($c);
  $i = curl_getinfo($c);
  curl_close($c);
  unset($c);

  $r = array();
  $r['status'] = string($i['http_code']);
  $r['type'] = $i['content_type'];
  $r['rels'] = http_rels($h, $url);
  return $r;
}
?>