Pass id getting from URL to many function in codeigniter

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PHP

CodeIgniter

I am getting an ID from a url like:

<?php echo base_url();?>Product/product/<?php echo $product->id;?>"

In my sidebar on the same function[view -> Product/product] I am getting it correctly. but when I click some other function in my sidebar the Id is not comming like:

What I have tried:

<pre lang="PHP">public function Product($id)
{
     $this->data['product'] = $this->prod->get_product($id);
    $this->load->view('products/header');
    $this->load->view('products/topnav');
    $this->load->view('products/sidebar',$this->data);
    $this->load->view('products/home',$this->data);
    $this->load->view('products/footer');
}

it is working on this page as expected, but when I jump to different function in my sidebar the id is not working because it is not getting it... like:

public function Data()
{
    $id=$this->Product($id);
    $this->data['product'] = $this->prod->get_product($id);
     $this->load->view('products/header');
    $this->load->view('products/topnav');
    $this->load->view('products/sidebar', $this->data);
    $this->load->view('products/data');
    $this->load->view('products/footer');

}

What I want: How to get the Id which I pass above to all my sidebar functions.