javascript与php使用json传递数据

<script>
function loadDoc(file,async=true){
if(window.XMLHttpRequest){  // code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}else{  // code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
if(async === true){
xmlhttp.onreadystatechange = function(){
    if(xmlhttp.readyState < 4){
        // 加载中
    }else if (xmlhttp.readyState == 4 && xmlhttp.status == 200){
        // 成功
        xmlDoc=xmlhttp.responseText;
        return xmlDoc
    }else{
        // 失败
        xmlhttp.abort()
        return
    }
}
}
xmlhttp.open("POST",file,async);
xmlhttp.setRequestHeader("Content-type", "application/json");
var data = {
name:'lee'
}
var json = JSON.stringify(data)
xmlhttp.send(json);
if(async === false){
xmlDoc=xmlhttp.responseText;
return xmlDoc
}
}
var data = loadDoc('http://localhost/test.php',false)
console.log(data)
</script>

<?php
header('access-control-allow-origin:*');
header('Access-Control-Allow-Headers:WWW-Authenticate,Authorization,Set-Cookie,X-Requested-With, Accept, Accept-Version, Content-Length, Content-MD5, Content-Type, Date, X-Api-Version');
$json = file_get_contents('php://input');
echo $json;