chromium/third_party/blink/web_tests/http/tests/eventsource/resources/echo-url.php

<?php
header("Content-Type: text/event-stream");
$url = $_SERVER["REQUEST_URI"] ?? null;
$id = $_SERVER["HTTP_LAST_EVENT_ID"] ?? null;

echo "id: 77\n";
echo "retry: 300\n";
echo "data: url = " . $url . ", id = " . $id . "\n\n";
?>