/** * {@inheritdoc} */ public function jsonSerialize() { $expires_at = null; if ($this->expires_at instanceof JsonSerializable) { $expires_at = $this->expires_at->jsonSerialize(); } elseif ($this->expires_at instanceof DateTimeInterface) { $expires_at = $this->expires_at->getTimestamp(); } return ['session_id' => $this->session_id, 'user_id' => $this->user_id, 'expires_at' => $expires_at]; }