function discover($target_url)
{
$webmention_endpoint = NULL;
$response_body = http\request("GET {$target_url}", array(), array(), $response_headers);
if (isset($response_headers['link'])) {
$links = link_header\parse($response_headers['link']);
if (isset($links['http://webmention.org/'])) {
$webmention_endpoint = $links['http://webmention.org/'][0]['uri'];
} elseif (isset($links['webmention'])) {
$webmention_endpoint = $links['webmention'][0]['uri'];
}
}
if (!is_null($webmention_endpoint)) {
return $webmention_endpoint;
} elseif (preg_match('#<link href="([^"]+)" rel="http://webmention.org/" ?/?>#i', $response_body, $matches) or preg_match('#<link rel="http://webmention.org/" href="([^"]+)" ?/?>#i', $response_body, $matches)) {
return $matches[1];
}
}
)
[http://example.net/relation/other] => Array
(
[0] => Array
(
[uri] => http://example.org/
)
)
)
*/
// Examples that simple regex based parsers fail on:
print_r(link_header\parse('<http://example.com/TheBook/chapter1>; rel="previous"; title="start, index"'));
/*
Array
(
[previous] => Array
(
[0] => Array
(
[uri] => http://example.com/TheBook/chapter1
[title] => start, index
)
)
)
*/
