html:
<table>
<tr><form name="form1" action="{:url('/index/index/addexcel')}" method="post" enctype="multipart/form-data">
<td><input name="file_stu" type="file" id="file"/></td><td>
<input type="submit" value="导入" name=""/>
</form></td></tr>
</tr>
</table>

index.php:
if (!empty($_FILES)) {
$tmp_file = $_FILES ['file_stu'] ['tmp_name'];
}
$file_types = explode ( ".", $_FILES ['file_stu'] ['name'] );
$file_type = $file_types [count ( $file_types ) - 1];

/*鍒ゅ埆鏄笉鏄�.xls鏂囦欢锛屽垽鍒槸涓嶆槸excel鏂囦欢*/
if (strtolower ( $file_type ) != "xlsx" && strtolower ( $file_type ) != "xls")
{
$this->error ( '涓嶆槸Excel鏂囦欢锛岄噸鏂颁笂浼�' );
}


报错：未定义数组索引【file_stu】