将选定的值从下拉列表添加到数据库angularjs php mysql

Question

我有一个下拉列表，我可以通过ng_model指令（selectedName）访问所选名称，但我的问题是，当我尝试将所选选项值传递给数据库时，它传递一个空值，查询执行和文本框值正确传递的问题是使用下拉选项值..出了什么问题..在控制器中或使用php代码mysqli_real_escape_string部分。它很困惑..任何帮助

<select data-ng-model="selectedName" ng-options="item for item in names">
</select>

var app = angular.module('myApp', []);
app.controller('myCtrl',  function($scope)  {
$scope.names = ["7G", "8G", "13G", "15G", "23G","26G"];


   app.controller("usercontroller", function($scope, $http){
    $scope.insertData = function(){
        $http.post(
            "insert.php",
            {'selectedName':$scope.selectedName, 
'selectedProject':$scope.selectedProject,  'user':$scope.user}
        ).success(function(data){
            alert(data);
        });
    }


$connect = mysqli_connect("localhost","root","","microlinks");  
$data = json_decode(file_get_contents("php://input"));
if(count($data) > 0){
$frequency = mysqli_real_escape_string($connect, $data->selectedName);
$project = mysqli_real_escape_string($connect, $data->selectedProject);
   $user = mysqli_real_escape_string($connect, $data->user);


$query = "insert into links(frequency,project,user,date) values ('$frequency','$project', '$user',)";

if(mysqli_query($connect, $query))
{
    echo "Hello World";
}
else
{
    echo 'Error';
}
}