编码器分页-数组变量在第2页上为空

我正在搜索页面上工作，因为搜索是基于数组$s_id。使用某个输入值进行搜索后，搜索结果将与分页链接一起完美地显示出来。(分页链接也很完美。如果我有6个结果和per_page是2，所以它显示3页链接)。

现在我的问题是，一旦我点击第2页，它显示空页，我尝试在第2页打印$s_id，然后数组显示像Array ( [0] => )，这意味着在第2页$s_id有一些其他的值。

public function index()
        {        
        $s_id = array();
        $skills = $this->input->post('skills');
        //pagination settings
        $config['per_page'] = 2;
        $config['base_url'] = site_url('search');
        $config['first_url'] = site_url('search/').'1';
        $config['use_page_numbers'] = TRUE;
        $config['num_links'] = 3;
        $config['uri_segment'] = 2;
        $config['cur_tag_open'] = "<li><span><b>";
        $config['cur_tag_close'] = "</b></span></li>";
        $config['full_tag_open'] = '<ul class="pagination pagination-large">';
        $config['full_tag_close'] = '</ul>';
        $config['prev_tag_open'] = '<li>'; 
        $config['prev_tag_close'] = '</li>';
        $config['next_tag_open'] = '<li>';
        $config['next_tag_close'] = '</li>';
        $config['num_tag_open'] = '<li>';
        $config['num_tag_close'] = '</li>';
        $config['cur_tag_open'] = '<li class="active"><a>';
        $config['cur_tag_close'] = '</a></li>';
        $page = $this->uri->segment(2);
        $limit_end = ($page * $config['per_page']) - $config['per_page'];
        if ($limit_end < 0){
            $limit_end = 0;
        }
        if($skills == TRUE || $this->uri->segment(2) == TRUE){
            $s_id = explode(',', $skills[0]);
            if($s_id){
              $filter_session_data['skill_id_selected'] = $s_id;
            }else{
              $s_id = $this->session->userdata('skill_id_selected');
            }
            $data['skill_id_selected'] = $s_id;
            if(isset($filter_session_data)){
                $this->session->set_userdata($filter_session_data);
            }
            // print_r($s_id); exit();                     //commented
            // $s_id = array('2D Design','3D Design');     //commented
            $data['count_user'] =  $this->m_results->count_users($s_id);
            $config['total_rows'] = $data['count_user'];
            $data['freelancers'] = $this->m_results->search_people($s_id,$config['per_page'],$limit_end);
            $this->pagination->initialize($config);
            $this->load->view('include/header');
            $this->load->view('search',$data);
            $this->load->view('include/footer');
        }else{  
            $this->load->view('include/header');
            $this->load->view('search');
            $this->load->view('include/footer');
        }
}  

public function search_people($s_id,$limit_start,$limit_end)
{
    $this->db->from('search_result');
    if($s_id){
        $this->db->where("FIND_IN_SET('$s_id[0]', skills) != ", 0);
        for($x=1; $x < count($s_id); $x++) {
            $this->db->or_where("FIND_IN_SET('$s_id[$x]', skills) != ", 0);
        } 
    }
    $this->db->limit($limit_start, $limit_end);
    $query = $this->db->get();
    return $query->result_array();
}

public function count_users($s_id=null)
{
    if($s_id){
        $this->db->where("FIND_IN_SET('$s_id[0]', skills) != ", 0);
        for($x=1; $x < count($s_id); $x++) {
            $this->db->or_where("FIND_IN_SET('$s_id[$x]', skills) != ", 0);
        } 
    }
    $query = $this->db->get();
    return $query->num_rows();
}  

请帮我解决这个问题