yii renderPartial view contain two blank lines

I try to modify someone yii framework project, when i renderPartial


$this->renderPartial('view');

in the view.php


<?php

echo 'phase1';

?>

in the browse it shows phase1 in the first line, but in the page source code it starts with two blank lines

I don’t know where those blank lines come from, and how to delete those lines.