cloudfront_cookie.php

<?php
require_once __DIR__ . "/vendor/autoload.php";

$cloudFront = new \Aws\CloudFront\CloudFrontClient([
    'region'  => 'us-west-2',
    'version' => '2014-11-06'
]);

$resourceKey = CloudfrontのURL;
$expires = time() + クッキーの有効期限;

// ポリシーの設定
$customPolicy = <<<POLICY
{
    "Statement": [
        {
            "Resource": "{$resourceKey}",
            "Condition": {
                "DateLessThan": {"AWS:EpochTime": {$expires}}
            }
        }
    ]
}
POLICY;

$signedCookieCannedPolicy = $cloudFront->getSignedCookie([
      'policy' => $customPolicy,
      'private_key' => Cloudfrontキーペアのプライベートキーファイルのパス,
      'key_pair_id' => CloudfrontキーペアID
]);