如何将ID（编号）添加到Codeigniter URL

I like to preface this question by apologizing for being noob.

For codeigniter URL, format goes: example.com/class/function/ID

If I were to have the urls below

website.com/books/chapter/1

website.com/books/chapter/2

I know how to create class named "books" under which I would create public function "chapter", so...

public funtion chapter() {
$this->load->view("content");
}

How would I add the ID's 1 and 2, assuming the only difference between the two website is I would have:

1.png within my "content" for website.com/books/chapter/1 and

2.png within my "content" for website.com/books/chapter/2, with 2.png replacing where 1.png was supposed to be.

Thanks!

Since you are using this URL: website.com/books/chapter/2, you are already passing the id after the last slash. Therefore your controller method should receive that ID as a parameter like this:

Controller:

public function chapter($id) {
    $data["image_id"] = $id;
    $this->load->view("content", $data);
}

View:

<img src="<?= $image_id ?>.png">

    Controller:

    public function chapter() {
        $data["image_id"] = $this->uri->segment(3); //since your ID(number) is in third segment so 3
        $this->load->view("content", $data);
    }

   View: 
     <a href="siteurl/controller/method/<?php echo $image_id;?>"><img src="<?=  $image_id ?>.png"></a>

for more info on URI class https://ellislab.com/codeigniter/user-guide/libraries/uri.html

The ids are just the method parameters. You can get it by passing the parameter in your method.

In the controller:

public function chapter($id) {
    $data["image_id"] = $id;
    $this->load->view("your_view", $data);
}

In your view:

<img src="<?php echo $image_id;?>.png"/>