当我单击类member-update-button的一个button时，下面的alert会提示我"收到错误，兄弟"，即error回调函数正在被调用。知道为什么吗？没有错误打印到控制台。以后，我该如何调试才能自己找到原因？我如何获得更多关于它失败原因的信息？
HTML:
<form method="POST" action="../wp-content/themes/allytics_theme/management/member_update.php" enctype="multipart/form-data">
<div class="modal fade" id="member-modal">
<div class="modal-dialog">
<div class="modal-content">
<div class="modal-header">
<div class="row">
<div class="col-xs-12 col-sm-12 col-md-12 col-lg-12">
<h2></h2>
</div>
</div>
</div>
<div class="modal-body">
<div class="row">
<div class="col-xs-12 col-sm-3 col-md-3 col-lg-3">
Full name:
</div>
<div class="col-xs-12 col-sm-9 col-md-9 col-lg-9">
<input type="text" name="fullname" value="">
</div>
</div>
<div class="row">
<div class="col-xs-12 col-sm-3 col-md-3 col-lg-3">
Title:
</div>
<div class="col-xs-12 col-sm-9 col-md-9 col-lg-9">
<input type="text" name="title" value="">
</div>
</div>
<div class="row">
<div class="col-xs-12 col-sm-3 col-md-3 col-lg-3">
Bio (approx 150 chars):
</div>
<div class="col-xs-12 col-sm-9 col-md-9 col-lg-9">
<input type="textarea" name="bio" value="">
</div>
</div>
<div class="row">
<div class="col-xs-12 col-sm-3 col-md-3 col-lg-3">
Sort order:
</div>
<div class="col-xs-12 col-sm-9 col-md-9 col-lg-9">
<input type="textarea" name="sord" value="">
</div>
</div>
<div class="row">
<div class="col-xs-12 col-sm-3 col-md-3 col-lg-3">
Pic:
</div>
<div class="col-xs-12 col-sm-9 col-md-9 col-lg-9">
<input type="file" name="pic">
</div>
</div>
</div>
<div class="modal-footer">
<div class="row">
<div class="col-xs-12 col-sm-3 col-md-3 col-lg-3">
<!-- empty space -->
</div>
<div class="col-xs-12 col-sm-9 col-md-9 col-lg-9">
<button type="button" class="member-update-button wp-core-ui button-primary" id="remv-btn">Remove</button>
<button type="button" class="member-update-button wp-core-ui button-primary">Add</button>
</div>
</div>
</div>
<input type="hidden" name="memberAction" value="" />
</div>
</div>
</div>
</form>
Javascript：
jQuery('.member-update-button').click( function() {
var parentForm = jQuery(this).closest('form');
var formUrl = parentForm.attr('action');
var formMethod = parentForm.attr('method');
var postData = parentForm.serializeArray();
jQuery.ajax(
{
url: formUrl,
type: formMethod,
dataType: 'json',
data: postData,
success: function(retmsg)
{
alert(retmsg); // test for now
},
error: function ( )
{
alert("got an error, bro"); // test for now
}
}
);
} );
PHP:
<?php
echo json_encode("here's the return message");
?>
try:
echo json_encode(array("here's the return message"));