If the alleged developmentally disabled person is within the state and is able to attend, he shall be present at the hearing. If he is unable to attend by reason of physical or other inability, such inability shall be evidenced by the affidavit or certificate of a duly licensed medical practitioner as provided in Section 1825 of the Probate Code. Such affidavit or certificate shall be filed no later than 10 days prior to the time of the hearing.