SessionCacheContext.php

<?php

namespace Drupal\Core\Cache\Context;

use Drupal\Component\Utility\Crypt;

/**
 * Defines the SessionCacheContext service, for "per session" caching.
 *
 * Cache context ID: 'session'.
 */
class SessionCacheContext extends RequestStackCacheContextBase {
    
    /**
     * {@inheritdoc}
     */
    public static function getLabel() {
        return t('Session');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getContext() {
        return Crypt::hashBase64($this->requestStack
            ->getSession()
            ->getId());
    }

}