Codeigniter - Interact with Database using Active Records

user.php

<?php

class User extends CI_Controller {

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

		$this->load->database();
	}

	public function insert($username, $password) {

		$data = array(
			"username" => $username,
			"password" => $password
		);

		$this->db->insert("users", $data);

		echo "Inserted";
	}

	public function select() {

		$result = $this->db->get("users")->result_array();

		$this->load->library("table");

		echo $this->table->generate($result);
	}

	public function update($username, $password) {

		$this->db->where("username", $username);
		$data = array("password" => $password);

		$this->db->update("users", $data);

		echo "Updated";
	}

	public function delete($user) {

		$this->db->where("username", $user);
		$this->db->delete("users");

		echo "Deleted";
	}
}