PHP 楽天ショッピングの商品情報を取得するには？

<?php
$params = [
  'applicationId' => [アプリID],
  'keyword'       => [キーワード],
  'sort'          => '+itemPrice',
];
$url = 'https://app.rakuten.co.jp/services/api/IchibaItem/Search/20220601?'.http_build_query($params);

$options = [
  CURLOPT_URL            => $url,
  CURLOPT_HTTPGET        => true,
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_HTTPHEADER     => [
    'Host:' => 'app.rakuten.co.jp',
  ],
  CURLOPT_TIMEOUT        => 3,
];
$curl = curl_init();
curl_setopt_array($curl,$options);
$res = curl_exec($curl);
if (false !== $res) {
  $json = json_decode($res);
  var_dump($json);
}