php – Jquery .serialize()不处理下拉列表的值？

<form id="contactform">
    <label for="name">Name</label> 
    <input type="text" id=name name=name placeholder="First and last name" tabindex="1" />

    <label for="phonenumber">Phone Number</label> 
    <input type="text" id=phonenumber name=phonenumber placeholder="Please enter your phone number" tabindex="2" />

    <label for="email">Email</label> 
    <input type="text" id=email name=email placeholder="example@domain.com" tabindex="3" />

    <label for="dropdown">Please Confirm:</label> 
        <select>
            <option value="question" selected="selected">I have a question</option>
            <option value="attending">I am attending</option>
            <option value="not-attending">I am not attending</option>
        </select>


    <label for="comment">Your Message</label>
        <textarea name="comment" id=comment name=comment placeholder="Enter something here,can't think" tabindex="5"></textarea> 

    <input name="submit" type="submit" id="submit" tabindex="6" value="Send Message"/>

</form>

这就是我如何序列化它：

$('#contactform').submit(function() {
    var query = $(this).serialize();

    $.ajax({
        type: "POST",url: "send.php",data: query,success: function(data) { // rest of function

最后我用来将值设置为变量的PHP位是：

$dropdown     = $_POST['dropdown'];

一个示例标题是name = sgrggr& phonenumber = 55555555555& email=me@me.comu0026amp; comment = quick test所以我不知道为什么下拉值没有被提取.

谢谢你的帮助.