$params */ public static function canonicalize(array $params, string $apiKey): string { $pairs = []; foreach (array_merge($params, ['key' => $apiKey]) as $k => $v) { $values = is_array($v) ? $v : [$v]; sort($values, SORT_STRING); foreach ($values as $vv) { $pairs[] = rawurlencode((string) $k) . '=' . rawurlencode((string) $vv); } } sort($pairs, SORT_STRING); return implode('&', $pairs); } /** * HMAC-SHA256 hex signature of `GET/api/v1/og\n`. * * @param array $params */ public static function sign(array $params, string $apiKey, string $hmacSecret): string { return hash_hmac('sha256', 'GET/api/v1/og' . "\n" . self::canonicalize($params, $apiKey), $hmacSecret); } /** * Build a ready-to-use signed OG image URL. * * Array params are encoded as `key[0]=`/`key[1]=` (PHP bracket syntax) so * the server's query parser reconstructs them as arrays. * * @param array $params */ public static function signedUrl( array $params, string $apiKey, string $hmacSecret, string $baseUrl = self::DEFAULT_BASE_URL, ): string { $all = array_merge($params, [ 'key' => $apiKey, 's' => self::sign($params, $apiKey, $hmacSecret), ]); return $baseUrl . '?' . http_build_query($all, '', '&', PHP_QUERY_RFC3986); } }