upload multiple image di codeigniter

gan, mau tanya neh, gimana sih cara upload image dengan lebih dari satu input menggunakan codeigniter dan database mysql. aku sudh coba gan cuman imagenya gak ke upload nilainya kosong jadi filenamenya gk kebaca. terima kasih gan.

 function uploadcobalagi(){

		$this->load->library('upload');

		$this->upload->initialize(array(
			'upload_path'=>"./_upload/image/tdp",
			'allowed_types'=>"./gif|jpg|png|jpeg"));

		$this->load->library('upload',$config);


		$this->upload->do_upload("gambar");
			$upload = $this->upload->data();
			$data =  array(
			'gambar1'=> $upload['file_name'].$this->input->post('[file_name]'),
			'gambar2'=> $upload['file_name'].$this->input->post('[file_name]'));
			$query = $this->pemohon->update_image($data);
			redirect(base_url('pemohon_c/ajukan_izin'));

		}

<form action="<?php echo base_url('pemohon_c/uploadcobalagi');?>" method="POST" name="uploadberkas_ijin">
<tr>
<td>gambar</td>
		<td>
			<input type="file" name="gambar[]" multiple="multiple" ></td>
		</td>
	</tr>

<tr>
<td>gambar</td>
		<td>
			<input type="file" name="gambar[]" multiple="multiple"></td>
		</td>
	</tr>
<tr>

<hr>
<input type="submit" name="submit" value="Upload" class="btn btn-lg btn-primary">
<a href="<?php echo base_url('pemohon_c/galery');?>">
	<input type="button" value="batal" class="btn btn-lg btn-danger">

</a>
</form>

function update_image($data){
		$query = $this->db->insert('cobagambar',$data);
		return $query;
	}