การใช้งาน captcha มีปัญหาเวลาเช็ค time()-7200 , php-codeigniter

# function floor(); ปัดทศนิยมออก
$this->captcha->_insert( floor($captcha['time']), $this->input->ip_address(), $captcha['word'] );

$checking = $this->db->where(.....)->get(....)->row_array();
if ( time() > $checking['time'] ) {
    # error
}

		$vals = array(
			'word' => rand_captcha(6),
			'img_path' => './captcha/',
			'img_url' => 'http://localhost/apps/captcha/',
			'font_path' => './assets/fonts/chunkfive-webfont.ttf',
			'img_width' => '150',
			'img_height' => 40,
			'expiration' => 900
		);

		$captcha = create_captcha($vals);
		$this->session->set_userdata('captchaWord', $captcha['word']);
		$data['captcha']=$captcha['image'];
		$this->load->view('captcha-view', $data);

public function verify()
	{
		$this->load->library('form_validation');
		$this->form_validation->set_error_delimiters('<p class="error">', '</p>');
		$this->form_validation->set_rules('details', "Description", 'trim|required|xss_clean');
		$this->form_validation->set_rules('captcha', "Captcha", 'trim|required|callback_captcha_check');
		$userCaptcha = set_value('captcha');
		$word = $this->session->userdata('captchaWord');
		if($this->form_validation->run() == FALSE)
		{
			$this->test();
		}
		else
		{
			$this->session->unset_userdata('captchaWord');
			$data = array(
				'details' => $this->input->post('details', TRUE),
				'active' => 'Y',
				'ip' => $this->input->ip_address(),
				'create_by' => $this->sess['username']
			);

			$this->db->trans_begin();

			$this->db->set('created', 'NOW()', FALSE);
			$this->db->insert('mytable', $data);

			if ($this->db->trans_status() === FALSE)
			{
				$this->db->trans_rollback();
				$msg=notification('error', $this->db->last_query());
			}
			else
			{
				$this->db->trans_commit();
				$msg=notification('success', 'Insert Record has been successfully. # '.$this->db->affected_rows().' effected.');
			}
			$this->session->set_flashdata('message', $msg);
			redirect('captcha/index');
		}
	}

	function captcha_check()
	{
		if($this->input->post('captcha') != $this->session->userdata('captchaWord'))
		{
			$this->form_validation->set_message('captcha_check', 'Wrong captcha code!');
			return false;
		}
		return true;
   }