如何在下拉选择菜单上添加验证？

Question

我如何在下拉选择菜单上添加验证我有代码，我正在处理，但问题是没有工作没有显示错误消息。我想显示错误消息，如果下拉选择值不应该在点击添加到购物车按钮之前选择？

if(isset($_REQUEST['check'])){
if (isset($_POST['size']) && $_POST['size'] == '' ) {
echo 'Error, select category';
exit;
}}

<form action="" id="size1" name="size1" method="post"> 
<select style="background-color:#CCC" 
name="size" id="size"  onchange="this.form.submit();" >
<option value="">Select</option>
<option <?php if ($_POST['size'] == 'Small') 
print 'selected '; ?>  value="Small">Small</option>
<option <?php if ($_POST['size'] == 'Medium') 
print 'selected '; ?> value="Medium">Medium</option>
<option  <?php if ($_POST['size'] == 'Large') 
print 'selected '; ?> value="Large">Large</option>
<option   <?php if ($_POST['size'] == 'XL')
print 'selected '; ?> value="XL">XL</option>
</select>

<input type="button" class="button1" name="check" 
value="Add To Cart" onclick="addtocart(<?php echo $row3['id'];?>);" />
</form

Answer 1

请试试它的工作

应该是这样的

<?php
    if($_POST['country']=="0")
    {
        echo 'Error, select category';
        //exit;
    }
?>
<form action="" id="size1" name="size1" method="post">
<select style="background-color:#CCC" 
name="size" id="size"  onchange="this.form.submit();" >
  <option value="0">Select</option>
  <option <?php if ($_POST['size'] == 'Small') 
print 'selected '; ?>  value="Small">Small</option>
  <option <?php if ($_POST['size'] == 'Medium') 
print 'selected '; ?> value="Medium">Medium</option>
  <option  <?php if ($_POST['size'] == 'Large') 
print 'selected '; ?> value="Large">Large</option>
  <option   <?php if ($_POST['size'] == 'XL')
print 'selected '; ?> value="XL">XL</option>
</select>
<input type="button" class="button1" name="check" 
value="Add To Cart" onclick="addtocart(<?php echo $row3['id'];?>);" />
</form>

Answer 2

在这里对html进行一些更改

<option value="0">Select</option>

和这样的功能来检查

function check_selected_or_not(){
var check_selected = jQuery('#size').val();
if (check_selected == 0){
    alert('Please select');
}else{
    alert('sucess');
}

}

Answer 3

如果我没有弄错您的问题，您希望在提交表单之前进行验证吗？如果是，则需要使用客户端验证：

http://docs.jquery.com/Plugins/validation#Example