注意：未定义的索引：php中的用户名和密码[重复]

Question

This question already has an answer here:

• “Notice: Undefined variable”, “Notice: Undefined index”, and “Notice: Undefined offset” using PHP 28 answers

I'm working with db connection, from what it looks like to me when I finish writing it on sublime there's no error. so, I decided to write localhost/*folder*/*filename*.php in my browser to check the connection and suddenly the browser display;

Notice: Undefined index: username in C:\xampp\htdocs\Login\login.php on line 4 Notice: Undefined index: pincode in C:\xampp\htdocs\Login\login.php on line 5 {"success":false}

<?php
    $con = mysqli_connect("localhost", "root", "", "test");

    $Username = $_POST["username"];
    $Pincode = $_POST["pincode"];

    $statement = mysqli_prepare($con, "SELECT * FROM users WHERE username = ? AND pincode = ?");
    mysqli_stmt_bind_param($statement, "ss", $Username, $Pincode);
    mysqli_stmt_execute($statement);

    mysqli_stmt_store_result($statement);
    mysqli_stmt_bind_result($statement, $id, $Username, $Pincode);

    $response = array();
    $response["success"] = false;  

    while(mysqli_stmt_fetch($statement)){
        $response["success"] = true;  
        $response["id"] = $id;
        $response["username"] = $Username;
        $response["pincode"] = $Pincode;
    }

    echo json_encode($response);
?>

</div>

Answer 1

You want to check if Username and pincode were sent before querying the db. If they are not passed then your query doesn't have to be run.

if(isset($_POST['username']) && isset($_POST['pincode'])){
   $con = mysqli_connect("localhost", "root", "", "test");

   $Username = $_POST["username"];
   $Pincode = $_POST["pincode"];

   ... etc.
} else {
   echo "Username or pincode missing";
}