Php 如何在CodeIgniter 3.1.1中使用Database Forge类

现在我正在使用CodeIgniter 3.1.1开发一个新的应用程序，我需要通过添加新列或删除现有列来自定义数据库列。我已经阅读了CodeIgniter文档，我发现了Database Forge，但是当我试图使用和遵循文档时，我遇到了一些错误！有人能帮我吗

<?php 

class Setting extends CI_Controller{
    function __construct(){
        parent::__construct();      
        $this->load->model('m_stock');
        if($this->session->userdata('status') != "login"){
            redirect(base_url("login"));
        }
        $forge = \Config\Database::forge();
    }

    function index(){

    }

    function tambah_cabang(){
        $fields = [
            'cabang_3' => ['type' => 'TEXT']
        ];
        $forge->addColumn('barang', $fields);
    }
}

---

我有它为我的用户_主表，调整你需要的

<?php

namespace App\Database\Migrations;

use CodeIgniter\Database\Migration;

class UserMaster extends Migration
{
    public function up()
    {
        $this->forge->addField([
            'id' => [
                'type' => 'INT',
                'auto_increment' => TRUE
            ],
            'name' => [
                'type' => 'VARCHAR',
                'constraint' => '50',
            ],
            'username' => [
                'type' => 'VARCHAR',
                'constraint' => '50',
            ],
            'password' => [
                'type' => 'VARCHAR',
                'constraint' => '50',
            ],
            'access_level' => [
                'type' => 'VARCHAR',
                'constraint' => '50',
            ],
        ]);
        $this->forge->addField("date_time timestamp DEFAULT CURRENT_TIMESTAMP");
        $this->forge->addPrimaryKey('id', TRUE);
        $this->forge->createTable('user_master');
    }

    //--------------------------------------------------------------------

    public function down()
    {
        $this->forge->dropTable('user_master');
    }
}

---

您似乎没有使用
$this->load->Database（）加载数据库类
也不是带有
$this->load->dbforge（）的forge类。加载Forge类的方式（
$Forge=\Config\Database:：Forge（）；
）就是在Codeigniter 4上加载它的方式。检查锻造厂的Codeigniter 3文档class@JavierLarroulet非常感谢！我读错了文件。我正在读代码点火器4！再次感谢！
<?php

namespace App\Database\Migrations;

use CodeIgniter\Database\Migration;

class UserMaster extends Migration
{
    public function up()
    {
        $this->forge->addField([
            'id' => [
                'type' => 'INT',
                'auto_increment' => TRUE
            ],
            'name' => [
                'type' => 'VARCHAR',
                'constraint' => '50',
            ],
            'username' => [
                'type' => 'VARCHAR',
                'constraint' => '50',
            ],
            'password' => [
                'type' => 'VARCHAR',
                'constraint' => '50',
            ],
            'access_level' => [
                'type' => 'VARCHAR',
                'constraint' => '50',
            ],
        ]);
        $this->forge->addField("date_time timestamp DEFAULT CURRENT_TIMESTAMP");
        $this->forge->addPrimaryKey('id', TRUE);
        $this->forge->createTable('user_master');
    }

    //--------------------------------------------------------------------

    public function down()
    {
        $this->forge->dropTable('user_master');
    }
}