json转换数组时中文为NULL解决方案

<?php
$json='[{"ZtdID":"100000","ZtdNo":"001 ","ZtdName":"1号店 ","Address":"XX市ZZ区YY路01号铺 ","Remark":"","AreaID":"01","ZtdTel":"0000-8888888","ZtdContact":"张三"},{"ZtdID":"100001","ZtdNo":"002 ","ZtdName":"1号店 ","Address":"XX市ZZ区YY路01号铺 ","Remark":"","AreaID":"01","ZtdTel":"0000-8888888","ZtdContact":"李三"}]';
var_dump(json_decode($json,true));

?>
输出为NULL
经仔细查看，是编码问题，求解？

iconv('gbk','UTF-8','我是中文要转换成json');

转吧.PHP的json 中文没有支持gbk gb2312的格式