Error Index undefined when i try send from android to mysql database

So currently i made menu to send a data from android to mysql database, but when i press send button that error always come,
here is my php code(addKomen.php)

<?php 
if($_SERVER['REQUEST_METHOD']=='POST'){

    //Getting values
    $nama = $_POST['nama'];
    $email = $_POST['email'];
    $isi = $_POST['isi'];

    //Creating an sql query
    $sql = "INSERT INTO email (nama,email,isi) VALUES ('$nama','$email','$isi')";

    //Importing our db connection script
    require_once('dbConnect.php');

    //Executing query to database
    if(mysqli_query($con,$sql)){
        echo 'Added Successfully';
    }else{
        echo 'Could Not Add';
    }

    //Closing the database 
    mysqli_close($con);
}

?>

So the problem is in my android code, because i type different variable
thanks for all the answer and then the problem is in my android code.
Best regards

You are not posting the data correctly, and to resolve the undefined index: nama use isset() to check whether the index you are trying to get is exist or not like:

if( isset( $_POST['nama'] ) )
{
    // This block will execute only if nama have some value in it.
}