updatecode File for Update Data in PHP

 <?php

include("mysqli_conn.php");

if (isset($_POST["updatedata"])) {

    $id = $_POST["update_id"];

    $fname = $_POST["fname"];

    $lname = $_POST["lname"];

    $course = $_POST["course"];

    $contact = $_POST["contact"];

    $sql = "UPDATE student SET fname='$fname', lname='$lname', course='$course', contact='$contact' WHERE id='$id'";

    if ($conn->query($sql) == TRUE) {

        echo "<script>alert(`Data Updated`);</script>";

        header("Location:index.php");

    } else {

        echo "<script>alert(`Data Not Updated`);</script>";

    }

}