Search a web page for a webmention endpoint and, if one exists, send a webmention to it.

sendWebmention.php

<?php

# Licensed under a CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
# http://creativecommons.org/publicdomain/zero/1.0/

function sendWebmention($source, $target) {

    $endpoint = false;

    $options = array(
        CURLOPT_URL => $target,
        CURLOPT_USERAGENT => 'adactio.com',
        CURLOPT_RETURNTRANSFER => TRUE,
        CURLOPT_HEADER => FALSE,
    );

    $curl = curl_init();
    curl_setopt_array($curl, $options);
    $body = curl_exec($curl);
    curl_close($curl);

    $dom = new \DOMDocument();
    @$dom -> loadHTML($body);
    $xpath = new \DOMXPath($dom);
    foreach ($xpath -> query('//*[local-name(.) = "a" or local-name(.) = "link"][contains(@rel, "webmention")]') as $node) {
        $endpoint = $node -> getAttribute("href");
        break;
    }

    if (empty($endpoint)) {
        return false;
    }

    if (!stristr($endpoint, '//')) {
        $components = parse_url($target);
        $domain = $components['scheme'].'://'.$components['host'];
        if (substr($endpoint, 0, 1) == '/') {
            $endpoint = $domain.$endpoint;
        } elseif (stristr($endpoint, '../')) {
            $path = $domain;
            $nesting = substr_count($endpoint,'../');
            $nesting++;
            $directories = explode('/', $target);
            for ($i = 1; $i < count($directories)-$nesting; $i++) {
                if (substr($path,0,-1) != '/') {
                    $path.= '/';
                }
                $path.= $directories[$i];
            }
            if (substr($path,0,-1) != '/') {
                $path.= '/';
            }
            $path.= $endpoint;
            $path = str_replace('../','',$path);
            $endpoint = $path;
        } else {
            $endpoint = $domain.'/'.$endpoint;
        }
    }

    $data = array(
        'source' => $source,
        'target' => $target
    );

    $options = array(
        CURLOPT_URL => $endpoint,
        CURLOPT_USERAGENT => 'adactio.com',
        CURLOPT_RETURNTRANSFER => TRUE,
        CURLOPT_POST => TRUE,
        CURLOPT_POSTFIELDS => $data,
        CURLOPT_TIMEOUT => 20
    );

    $curl = curl_init();
    curl_setopt_array($curl, $options);
    $response = curl_exec($curl);
    curl_close($curl);

    return;
    
}

?>