如果用户未从选择Box-PHP中选择值，如何限制用户提交表单

Question

我正在做一个项目，其中管理员有权添加新用户。

在“添加新用户”表单中，我有一个选择的“名称”框，它是从数据库中填充的。我想知道用户是否未从选择选项中选择任何指定，否则会报错，请选择指定或类似的东西。这是我的代码：

<select class="form-control" name="designation" id="designation" style="color:  black;" required>

    <option value="<?php echo $row['designation_id']; ?>">Please Select designation</option>

    <?php

    $sel_cus = "select designation_name ,designation_id from designation ";

    $res_cus = mysqli_query($connection, $sel_cus);

    while ($row = mysqli_fetch_array($res_cus)) { ?>

        <option value="<?php echo $row['designation_id ']; ?>"><?php echo $row['designation_name']; ?></option>

    <?php

}

?>

</select>

如果选择框的选择索引为0，即[请选择名称]，则会出现错误，请从列表中选择名称。需要善良的指导。

Answer 1

您正在访问$row变量，甚至在以下语句中也没有该变量，<option&nbsp;value="<?php&nbsp;echo&nbsp;$row['designation_id'];&nbsp;?>">Please&nbsp;Select&nbsp;designation</option>请将此声明替换为以下内容，<option&nbsp;value="">Please&nbsp;Select&nbsp;designation</option>选择要与所需属性一起使用的第一个选项的值应该为空白。参考此规范而且，如果您不希望出现错误，则只需required从select元素中删除属性即可。

Answer 2

您可以使用这种方法。<form action="" method="post" onsubmit="return validateForm()">&nbsp; &nbsp; <select class="form-control" name="designation" id="designation" style="color:&nbsp; black;" required>&nbsp; &nbsp; &nbsp; &nbsp; <option value="0">Please Select designation</option>&nbsp; &nbsp; &nbsp; &nbsp; <option value="1">designation 1</option>&nbsp; &nbsp; &nbsp; &nbsp; <option value="2">designation 2</option>&nbsp; &nbsp; </select>&nbsp; &nbsp; <input type="submit" value="Submit"></form><script>&nbsp; &nbsp; function validateForm(){&nbsp; &nbsp; &nbsp; &nbsp; var e = document.getElementById('designation');&nbsp; &nbsp; &nbsp; &nbsp; var selectedDesig = e.options[e.selectedIndex].value;&nbsp; &nbsp; &nbsp; &nbsp; if(selectedDesig == 0){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; alert('Please Select designation');&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return false;&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; return true;&nbsp; &nbsp; }</script>