Upload Excel Codeigniter Error double primary key

I want to insert data from Excel with codeigniter, but I found something difficult for me. When I upload file, there is a some data double in primary key. I try to check it first before upload with

Code:

   $cek=$this->m_admin->get_redudant($data['cells'][$i][2]);
   if ($cek==0) {
$this->m_admin->add($dataexcel);
redirect('home','refresh');
   }
   else{
    echo "something wrong";
   }  

Here is function upload file:

 

Code:

 function do_upload(){
$config['upload_path'] = './temp_upload/';
$config['allowed_types'] = 'xls';          
$this->load->library('upload', $config);                
if ( ! $this->upload->do_upload())
{
$data = array('error' => $this->upload->display_errors());
}
else
{
           $data = array('error' => false);
$upload_data = $this->upload->data();

           $this->load->library('excel_reader');
$this->excel_reader->setOutputEncoding('CP1251');

$file =  $upload_data['full_path'];
$this->excel_reader->read($file);
error_reporting(E_ALL ^ E_NOTICE);

$data = $this->excel_reader->sheets[0] ;
           $dataexcel = Array();
           $i=0;
for ($i = 1; $i <= $data['numRows']; $i++) {
                           if($data['cells'][$i][1] == '') break;
                           $dataexcel[$i-1]['nip'] = $data['cells'][$i][2];
                           $dataexcel[$i-1]['nama'] = $data['cells'][$i][1];
                           $dataexcel[$i-1]['nipbr'] = $data['cells'][$i][3];
                           $dataexcel[$i-1]['tempat'] = $data['cells'][$i][4];
                           $dataexcel[$i-1]['lahir'] = $data['cells'][$i][5];
                           $dataexcel[$i-1]['temp_kerja'] = $data['cells'][$i][6];
}

           delete_files($upload_data['file_path']);            
           $cek=$this->m_admin->get_redudant($data['cells'][$i][2]);


           if ($cek==0) {
$this->m_admin->add($dataexcel);
redirect('home','refresh');
           }
           else{
            echo "something wrong";
           }    
}

}

I want to manipulate data in primary key. If data is exist , I will add data random in the end of id like

Code:

   else{
           $x = rand(1, 1000);
           $dataexcel[$i-1]['nip'] = $data['cells'][$i][2]."$x";
   }

but it's not work , what should I do..