if else语句将数据从输入的数字插入到文本框中

Question

If user enter 50 at the quantity textbox, and must show "Do load into 3 ton lorry" in the type of lorry textbox and vice versa

<tr>
    <th>
        <center>Quantity:</center>
    </th>
    <td>
        <input type="text" name="quantity" />
    </td>
</tr>
<tr>
    <th>
        <center>Type of Lorry:</center>
    </th>
    <td>
        <input type="text" name="barcode" />
    </td>
    <?php
        if ($quantity > 40) echo "Do load into 3 ton lorry";
        else echo "Do load into 1 ton lorry";
    ?>
</tr>

Answer 1

PHP is server-side. Therefore, you should use javascript to response as you enter a number without reloading the page. For a solution, refer to https://www.w3schools.com/jsref/event_onkeypress.asp