Simple webmention entry point

webmention.php

<?php
/**
 * Receive webmention pings https://www.w3.org/TR/webmention/
 * 
 * @license Creative Commons https://creativecommons.org/publicdomain/zero/1.0/
 */

$statusURL = '';
$data = [];

$request = file_get_contents('php://input');
if ($request) {
    mb_parse_str($request, $data);
}

if (isset($data['source'])
	&& filter_var($data['source'], FILTER_VALIDATE_URL)
	&& isset($data['target'])
	&& filter_var($data['target'], FILTER_VALIDATE_URL)
) {

	/* TODO: Handle request data */

	if ($statusURL) {
		// Request was saved
		header($_SERVER['SERVER_PROTOCOL'] . ' 201 Created');
    		header('Location: ' . $statusURL);
		header('Content-type: text/plain');
		echo 'The Webmention is being processed. You can check on its status here: ' . $statusURL;
	} else {
		// Handle asynchronously
    		header($_SERVER['SERVER_PROTOCOL'] . ' 202 Accepted');
		header('Content-type: text/plain');
		echo 'The Webmention is being processed';
	}
} else {
    header($_SERVER['SERVER_PROTOCOL'] . ' 400 Bad Request');
}