Insert data

<?php
    $servername = "localhost";
    $username = "YUN";
    $password = "xxx";
    $dbname = "TestnaBaza";

    // naredi povezavo
    $conn = mysqli_connect($servername, $username, $password, $dbname);
    //preveri povezavo
    if (!$conn){
        die ("Povezava ni uspela" .mysqli_connect_error());
    }

    $response = array();
    $res = array();

    $json = _json_decode(file_get_contents('php://input'));

    if($json!=null){
        //$device = $json("YUN");
        $temperatura = "28"; //$json("26")
        $datum =date('Y-m-d-h-i-s') ; //$json("date")

    $sql = "INSERT INTO YunPodatki(temperatura,datum) VALUES(
    '$temperatura', '$datum')";

    if(mysqli_query($conn, $sql)){
        $response["code"] = 1;
        $response["message"] = "Uspesno shranjeno";
        echo json_encode($response);
    } else {
        $response["code"] = 2;
        $response["message"] = mysqli_error($conn);
        echo json_encode($response);
    }

    }else {

        echo "json error";
    }

    mysqli_close($conn);

    function _json_decode($string){
        if (get_magic_quotes_gpc()){
            $string = stripcslashes($string);
        }
        return json_decode($string.true);
    }
    ?>