Undefined variables at insert into value

<?php

require 'db.php';

if(isset($_POST['submit'])){





$DepName = $_POST['DepName'];
$Address = $_POST['Address'];
$PIC = $_POST['PIC'];
$Contact = $_POST['Contact'];
$RecordVisit = $_POST['RecordVisit'];
$Outlet = $_POST['Outlet'];
$JobTitle = $_POST['JobTitle'];
$Sales = $_POST['Sales'];
$JobDate = $_POST['JobDate'];
$Note = $_POST['Note'];
}

$result = $mysqli->query("SELECT * FROM villadata WHERE VillaID='VillaID'") or die($mysqli->error());

if ( $result->num_rows > 0 ) {
    
    $_SESSION['message'] = 'User already exists! Please try other username!';
    echo "User exist";
}

else{
$sql="INSERT INTO villadata(DepName,Address,PIC,Contact,RecordVisit,Outlet,JobTitle,Sales,JobDate,Note)
VALUES('$DepName','$Address','$PIC','$Contact','$RecordVisit','$Outlet','$JobTitle','$Sales','$JobDate','$Note')";

 if ( $mysqli->query($sql) ){

        $_SESSION['logged_in'] = true; 
        header("location: tables-data.php");

    }

  else {
        $_SESSION['message'] = 'Registration failed!';
        echo "Registration failed.";
    }

}
?>