addKey.php

<?php

    include_once 'common.php';

    if (isset($_GET['key'])) {
        $key = $_GET['key'];
        // Regex-based filter.
        if (isYouTubeDataAPIV3Key($key)) {
            $keysContent = file_get_contents(KEYS_FILE);
            $keys = explode("\n", $keysContent);
            // Verify that the YouTube Data API v3 key isn't already stored by the instance.
            if (!in_array($key, $keys)) {
                $httpOptions = [
                    'http' => [
                        'ignore_errors' => true,
                    ]
                ];
                $content = getJSON("https://www.googleapis.com/youtube/v3/videos?part=snippet&id=mWdFMNQBcjs&key=$key", $httpOptions, false);
                // The force secret is used to store the YouTube Data API v3 even if it's not having quota, as we assume that the trusted instance that send it to this one has checked that it has quota.
                if ($content['items'][0]['snippet']['title'] === 'A public video' || (isset($_GET['forceSecret']) && $_GET['forceSecret'] === ADD_KEY_FORCE_SECRET)) {
                    file_put_contents(KEYS_FILE, ($keysContent === '' || $keysContent === false ? '' : "\n") . $key, FILE_APPEND);
                    // Avoid sending another time the given key to all instances.
                    if (!isset($_GET['forceSecret'])) {
                        foreach (ADD_KEY_TO_INSTANCES as $addKeyToInstance) {
                            getRemote($addKeyToInstance . "addKey.php?key=$key&forceSecret=" . ADD_KEY_FORCE_SECRET);
                        }
                    }
                    echo 'YouTube Data API v3 key added.';
                } elseif ($content['error']['errors'][0]['reason'] === 'quotaExceeded') {
                    // As users can set `Queries per minute` quota to 0, we avoid denial-of-service by not considering them.
                    echo 'Not adding YouTube Data API v3 key having quota exceeded.';
                } else {
                    // This YouTube Data API API v3 keys isn't assigned or there is another error.
                    echo 'Incorrect YouTube Data API v3 key.';
                }
            } else {
                echo 'This YouTube Data API v3 key is already in the list.';
            }
        } else {
            echo "The key provided isn't a YouTube Data API v3 key.";
        }
    }