This is a simple example in Yii2.0 to understand how you can write a custom component and use it inside your app.(basic template)

Step1:Make a folder named "components" in your project root folder.

step2:

  write your custom component  inside components folder
 eg:MyComponent.php

namespace app\components;


use Yii;
use yii\base\Component;
use yii\base\InvalidConfigException;
 
class MyComponent extends Component
{
 public function welcome()
 {
  echo "Hello..Welcome to MyComponent";
 }
 
}

Step3:Add your component inside the config/web.php file

eg:

'components' => [
         
         'mycomponent' => [
         
            'class' => 'app\components\MyComponent',

            ],
           ]

Step4:You are done!. Now you can use your component method "welcome" inside any of your app controller actions.

   eg:controllers/TestController.php

namespace app\controllers;
use Yii;

class TestController extends \yii\web\Controller
{
    public function actionWelcome()
    {
       Yii::$app->mycomponent->welcome();
    }

}

Thanks. happy coding... Sirin K

Nintriva