media_model.php

<?php
class Media_model extends CI_Model
{
    private $table = 'media';

    private $store = [];

    function __construct()
    {
        parent::__construct();

        if(!empty($this->store)) {
            return;
        }

        $this->db->order_by('date', 'desc');
        $media = $this->db->get($this->table)->result_array();

        foreach($media as $file) {
            $this->store[$file['id']] = $file;
        }
    }

    public function all()
    {
        return $this->store;
    }

    public function limit($max = 25, $start = 1)
    {
        $this->db->limit($max, $start);

        $this->db->order_by('date', 'desc');
        return $this->db->get($this->table)->result_array();
    }

    public function byId($mediaId)
    {
        if(!$mediaId) {
            return;
        }

        return $this->store[$mediaId];
    }

    public function count()
    {
        $q = $this->db->get($this->table);
        return $q->num_rows();
    }
}