Php Codeigniter迁移自动和关键问题

我试图在Codeigniter中创建一个迁移文件，但当我运行它时，它会抛出一个错误，无论我做什么，我都无法让它运行

class Migration_Add_users extends CI_Migration {     

public function up()
{
        $this->dbforge->add_field(array(
            'USERS_id' => array(
                'type' => 'INT',
                'constraint' => 5,
                'auto_increment' => TRUE,
            ),
            'USERS_firstname' => array(
                'type' => 'VARCHAR',
                'constraint' => '100',
            ),
            'USERS_surname' => array(
                'type' => 'VARCHAR',
                'constraint' => '100',
            ),
            'USERS_email' => array(
                'type' => 'VARCHAR',
                'constraint' => '150',
                ),
            'USERS_password' => array(
                'type' => 'VARCHAR',
                'constraint' => '150',
                ),
            'USERS_password' => array(
                'type' => 'VARCHAR',
                'constraint' => '150',
                ),
            'USERS_created' => array(
                'type' => 'DATETIME',
                ),
        ));

        $this->dbforge->create_table('users');
        $this->dbforge->add_key('USERS_id', TRUE);
    }

    public function down()
    {
        $this->dbforge->drop_table('users');
    }
}

这就是错误所在

Error Number: 1075
Incorrect table definition; there can be only one auto column and it must be defined as a key

表格

CREATE TABLE `users` ( 
`USERS_id` INT(5) NOT NULL AUTO_INCREMENT, 
`USERS_firstname` VARCHAR(100) NOT NULL, 
`USERS_surname` VARCHAR(100) NOT NULL, 
`USERS_email` VARCHAR(150) NOT NULL, 
`USERS_password` VARCHAR(150) NOT NULL, 
`USERS_created` DATETIME NOT NULL ) DEFAULT 
CHARACTER SET utf8 COLLATE utf8_general_ci;

出现两次。

我需要运行

dbforge->add_key 

在

dbforge->create_table

一定有办法把它添加到

dbforge->add_field 

---

array

将USERS\u id设置为主键我需要运行dbforge->add\u键，然后再运行dbforge->create\u表-dam it！必须有一种方法将其添加到dbforge->add_字段数组是否需要在create table指令之前添加键？

dbforge->add_field