Pagination does not work when the application is not in the root directory

I am working on a [b]blog application[/b] with [b]Codeigniter 3.1.8[/b] and [b]AngularJS v1.7.8[/b].

The Dashboard of the application is "pure" Codeigniter, with Models, Controllers, and views, while the fronted is made up of JSONs managed and displayed by AngularJS. (I operated this clear [i]separation[/i] between back-end and front-end in order to enable "themeing".)

The posts are paginated. On the back-end, in the [i]Posts controller[/i], the posts list looks like this:

Code:

private function _initPagination($path, $totalRows, $query_string_segment = 'page') {
  //load and configure pagination
    $this->load->library('pagination');
    $config['base_url'] = "http://".$_SERVER['HTTP_HOST'] . $path;
    $config['query_string_segment'] = $query_string_segment;
    $config['enable_query_strings'] =TRUE;
    $config['reuse_query_string'] =TRUE;
    $config['total_rows'] = $totalRows;
    $config['per_page'] = 12;
    if (!isset($_GET[$config['query_string_segment']]) || $_GET[$config['query_string_segment']] < 1) {
        $_GET[$config['query_string_segment']] = 1;
    }
    $this->pagination->initialize($config);

    $limit = $config['per_page'];
    $offset = ($this->input->get($config['query_string_segment']) - 1) * $limit;

    return ['limit' => $limit, 'offset' => $offset];
}

public function index() {

  //call initialization method
    $config = $this->_initPagination("/", $this->Posts_model->get_num_rows());

    $data = $this->Static_model->get_static_data();
    $data['pagination'] = $this->pagination->create_links();
    $data['pages'] = $this->Pages_model->get_pages();
    $data['categories'] = $this->Categories_model->get_categories(); 

  //use limit and offset returned by _initPaginator method
    $data['posts'] = $this->Posts_model->get_posts($config['limit'], $config['offset']);

    // All posts
    $this->output->set_content_type('application/json')->set_output(json_encode($data,JSON_PRETTY_PRINT));
}

On the front-end, in AngularJS, I have:

Code:

// All posts
.controller('PostsController', ['$scope', '$http', function($scope, $http){

    //Get current page (?page=2, ?page=3 etc)
    const currPage = window.location.search;

    // Get all the posts on the current page
    $http.get('api/' + currPage).then(function(response) {

        //Categories
        $scope.categories = response.data.categories;

        // Posts
        $scope.posts = response.data.posts;

        // posts pagination
        $scope.pagination = response.data.pagination;

    });
}])

The problem is that the pagination does not work when the application is [b]not[/b] in the root directory (it is at www.examplesite.com/blog, not at www.examplesite.com).

I suppose it has something to do Codeigniter's base_url() but I have not been able to spot the bug and fix it.

How can I fix this issue?