Library Yii2 for Codeigniter

autoload.php

/*
| -------------------------------------------------------------------
|  Auto-load Libraries
| -------------------------------------------------------------------
| These are the classes located in system/libraries/ or your
| application/libraries/ directory, with the addition of the
| 'database' library, which is somewhat of a special case.
|
| Prototype:
|
|	$autoload['libraries'] = array('database', 'email', 'session');
|
| You can also supply an alternative library name to be assigned
| in the controller:
|
|	$autoload['libraries'] = array('user_agent' => 'ua');
*/
$autoload['libraries'] = array('Yii_Library');

third_party

Download archive yii2 framework : https://github.com/yiisoft/yii2-framework/archive/2.0.10.zip
masukan ke third_party : application\third_party\yii2

Yii_Library.php

<?php

define('YII_ENABLE_ERROR_HANDLER', false);

/**
 * Class Yii_Library
 * @package Libraries
 */

class Yii_Library
{

    /**
     * @var array $db_config
     */
    private $db_config;

    /**
     * @var string $yii_path
     */
    private $yii_path = 'third_party/yii2/Yii.php';

    /**
     * Yii_Library constructor.
     */
    public function __construct()
    {
        /**
         * @var array $db
         * @var string $active_group
         */
        require_once APPPATH.'config/database.php';
        $this->db_config = $db[$active_group];
        $this->init();
    }


    /**
     * @return void
     */
    public function init(){
        require APPPATH . $this->yii_path;
        new yii\web\Application([
            'id' => 'ci-app',
            'basePath' => APPPATH,
            'components' => [
                'db' => [
                    'class' => 'yii\db\Connection',
                    'dsn' => 'mysql:host='.$this->db_config['hostname'].';dbname='. $this->db_config['database'],
                    'username' => $this->db_config['username'],
                    'password' => $this->db_config['password'],
                    'charset' => 'utf8',
                    'tablePrefix' => $this->db_config['dbprefix']
                ]
            ]
        ]);
    }
}

much better