Quick Yii 2.0 debugging tip:
We recently made use of some Yii 2.0 widgets in a project being converted from Yii 1.1. On one page, we had a JUI Progress Bar widget being displayed as well as an ActiveForm widget. On initial tests, the progress bar (the first widget on the screen) was being printed at the very top of the page. A look at the HTML source revealed it was echo’ing the progress bar HTML at the very top of the HTML, even before the first tag. Looking at the page a little closer, a mistake was found – the ActiveForm widget didn’t have an end tag. Adding the end tag fixed it up.
We hope this saves someone some time down the road!