未捕获的TypeError：无法在delete_student中设置undefined的属性“value”

Question

error page 这是页面的图像错误 这是validation.js

 function delete_student(st_id){
            if(confirm("Do you want to delete the student?")){
                this.document.student_view.st_id.value = st_id;
                this.document.student_view.st_act.value= "delete_student";
                this.document.student_view.submit();
            }
        }

这是student.php

function delete_student(){
    $SQL = "DELETE FROM student WHERE st_id = $_REQUEST[st_id]";
    $rs= mysql_query($SQL) or die(mysql_error());
    if($rs)
    {
        header("Location:../student_view.php?msg=Student Deleted  succesfully");
    }
}
?> 

这是student_view.php

<?php 
while($data= mysql_fetch_assoc($rs))
{
?>
<tr>
    <td><?=$data['st_id']?></td>
    <td><?=$data['st_name']?></td>
    <td><?=$data['st_father']?></td>
    <td><?=$data['st_mobile']?></td>
    <td>Edit | <a href="Javascript:delete_student(<?=$data['st_id'] ?>)">Delete</a></td>
    </tr>
  <?php } ?>

</table>
<input type="hidden" name="act" />
<input type="hidden" name="st_id"> 
</form>
<?php include_once("includes/footer.php"); ?>

当我检查控制台时，我正在解决如下错误。

Uncaught TypeError: Cannot set property 'value' of undefined at delete_student

当我检查控制台时，我正在解决如下错误。

Uncaught TypeError: Cannot set property 'value' of undefined at delete_student