Yii::app()->User 无法使用 [ 未指定版本 ]

view文件index.php

<?php
echo 'abc<br>';

if (yii::app() != null)
{
    var_dump(yii::app()->user);
    echo '<br>';
}

echo 'def';
?>

输出结果: abc

日志并没有错误且显示'user'组件已经加载 
Loading "user" application component
in /data/home/qyu10131/htdocs/protected/views/site/index.php (12)
in /data/home/qyu10131/htdocs/protected/controllers/SiteController.php (28)
in /data/home/qyu10131/htdocs/index.php (13)

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