php的$_POST传值发现的小问题

<div>
<input type="text" placeholder="用户名" id="username" name="username">
</div>

$name=$_POST['username'];
$sql = "INSERT INTO `user` (`id`, `username`) VALUES (NULL, '$name')";
mysql_query($sql);

var param={
'username':$("#userame").val()||''
}
$.ajax({
url:"../php/register.manage.php",
type:'POST',
data:param,
dataType:"JSON",
success:function(result){
console.log(result);
},
error:function(){
console.log("error");
}
});