为什么总是出现未定义索引怎么解决呀

问题描述

<?php

include("connect/connect.php");

$xh=$_GET['xh'];

$sql="select xh,xm,xb,zymc from xsjbxxb where xh=".$xh;/lect host,user from user

$result=mysqli_query($conn,$sql);

while( $arr=mysqli_fetch_array($result) )

{

?>

<form id="form1" method="post" action="update_ok_1.php">

<table border="1" width="400" align="center" cellpadding="0" cellspacing="0">

<tr>

<td width="100">学号:</td>

<td><input type="text" name="xh" value="<?php echo $arr[0]; ?>"readonly></input></td>

</tr>

<tr>

<td>姓名:</td>

<td><?php echo $arr[1]; ?></td>

</tr>

<tr>

<td>性别:</td>

<td><?php echo $arr[2]; ?></td>

</tr>

<tr>

<td>专业名称:</td>

<td>

<?php echo $arr[3]; ?>

</td>

</tr>

<tr>

<td colspan="2" align="center"><input type="submit" name="sub1" value="添加">&nbsp;&nbsp;

<input type="reset" name="sub2" value="清空">

</td>

</tr>

<?php

}

?>

</form>

</table>

</body>

问题解答

xh字段是主键吗?