Json中的dataType:"json"问题

在如下代码中，只要设置dataType:"json", $ajax 中的success()就无法执行，直接被error:接管。这是为什么呢？？？（已设置所有charset=utf-8，DB的charset=gbk）
JS代码：

PHP代码：

返回的值是：["\u7701\u4e2d\u5fc3\u50a8\u84c4\u670d\u52a1\u5668","\u7701\u7535\u5b50\u6c47\u5151\u670d\u52a1\u5668","\u7701\u7535\u5b50\u5316\u670d\u52a1\u5668","\u4e09\u7ea7\u4e2d\u5fc3\u5c40\u670d\u52a1\u5668","\u4e09\u7ea7\u4e2d\u5fc3\u5c40\u670d\u52a1\u5668","\u901f\u9012\u670d\u52a1\u5668","\u7f51\u70b9\u4ee3\u6536\u4ed8\u670d\u52a1\u5668","\u793e\u533a\u670d\u52a1\u56681","\u793e\u533a\u670d\u52a1\u56682","\u4f9b\u7535\u4f9b\u6c34\u670d\u52a1\u5668","\u6606\u533a\u4fdd\u9669\u670d\u52a1\u5668","\u9752\u4e1c\u65d7\u4fdd\u9669\u670d\u52a1\u5668","\u4e8b\u540e\u4f1a\u8ba1\u670d\u52a1\u5668","\u4e00\u5361\u901a\u670d\u52a1\u5668","\u673a\u7968\u670d\u52a1\u5668","\u963f\u5c14\u4e01\u5357\u8857","\u6cbc\u6f6d"
不是标准的json格式，但已经echo json_encode()了啊，求帮助。