自我发布带有验证的Php代码

Question

I am currently working with an simple php code with validation and this is my code:

<form action="" method="post">
    <input type="text" name="name" id="name" placeholder="Name">
    <br>Number of Books:<select id="books" name="books">
    <option> 1 </option>
    <option> 2 </option>
    <option> 3 </option>
    <option> 4 </option>
    <option> 5 </option>
    <option> 6 </option>
    <option> 7 </option>
    <option> 8 </option>
    <option> 9 </option>
    <option> 10 </option>
</select>
</br>dutedate <input type="date" name="duedate" id="duedate" placeholder="duedate">
</br>borrow <input type="date" name="datebor" id="datebor" placeholder="dateborrowed">
</br>return <input type="date" name="ret" id="ret" placeholder="date returned">
<input type="submit" class="button" name="btnsubmit" value="Submit">
</form>
<?php
if (isset($_POST['btnsubmit']))
{
    $name = $_POST['name'];
    $duedate = date_create(($_POST['duedate']));
    $datebor = date_create(($_POST['datebor']));
    $ret = date_create(($_POST['ret']));
    $books = $_POST['books'];
    $NOWdate = new Datetime('now');
    if ($duedate  < $datebor)
    {
        echo "<script>alert('Wrong Input Error1')</script>";
        exit;
    }
    elseif ($datebor  > $ret)
    {
        echo "<script>alert('Wrong Input Error2')</script>";
        exit;
    }
    elseif ($datebor > $NOWdate )
    {
        echo "<script>alert('Wrong  Error3')</script>";
        exit;
    }
    elseif ($ret < $duedate)
    {
        $penalty = 0 ;
    }
    else
    {
        $penaltydays = date_diff($duedate,$ret) ;
        $diff_date = $penaltydays->format('%a');
        $penalty = $diff_date * $books * 10;
    }
}
?>
<p>Penalty: <?php echo $penalty ?></p>

When I try to run it, there is an error Undefined variable: penalty.

I am pretty sure that my validation codes are correct

How could I pass the penalty variable to the page itself.

I think it would resolve the error.

Answer 1

The problem is that the $penalty is only set after you submit the form. You should be able to fix this by simply moving the penalty paragraph inside your elseif/else blocks where a penalty should actually be shown.

...
elseif ($ret < $duedate)
{
    echo "<p>Penalty: 0</p>";
else
{
    $penaltydays = date_diff($duedate,$ret) ;
    $diff_date = $penaltydays->format('%a');
    $penalty = $diff_date * $books * 10;
    echo "<p>Penalty: $penalty</p>";
}

This way it will only be displayed if it has been calculated.

Side note, I don't think this will work the way you are expecting it to because your select options do not have value attributes. You need to add them like this:

<option value="1"> 1 </option>