// /index?r=site/index

echo Url::to(['site/index']);

// /index?r=site/index&src=ref1#name

echo Url::to(['site/index', 'src' => 'ref1', '#' => 'name']);

// the currently requested URL

echo Url::to();

// /images/logo.gif

echo Url::to('@web/images/logo.gif');

// images/logo.gif

echo Url::to('images/logo.gif');

// http://www.example.com/images/logo.gif

echo Url::to('@web/images/logo.gif', true);

// https://www.example.com/images/logo.gif

echo Url::to('@web/images/logo.gif', 'https');

// /index?r=site/index

echo Url::toRoute('site/index');

// /index?r=site/index&src=ref1#name

echo Url::toRoute(['site/index', 'src' => 'ref1', '#' => 'name']);

// http://www.example.com/index.php?r=site/index

echo Url::toRoute('site/index', true);

// https://www.example.com/index.php?r=site/index

echo Url::toRoute('site/index', 'https');

echo Yii::$app->urlManager->createUrl('site/index')