Mini Shell

<?php
include('include/connection.php');

if (isset($_POST['enquiry'])) {
    $name = $_POST['name'];
    $phone = $_POST['phone'];
    $email = $_POST['email'];
    $subject = $_POST['subject'];
    $message = $_POST['message'];

    if (isset($_POST['product']) && $_POST['product'] != '') {
        $product = $_POST['product'];
        $price = $_POST['price'];
        $sql = "INSERT INTO `book_query`(`product`, `name`, `email`, `phone`, `subject`, `message`) VALUES ('$product','$name','$email','$phone','$subject','$message')";
    } else {

        $sql = "INSERT INTO `contact`(`name`, `email`, `phone`, `subject`, `message`) VALUES ('$name','$email','$phone','$subject','$message')";
    }
    $res = mysqli_query($con, $sql);
    if ($res) {
        header("Location: " . $_SERVER['HTTP_REFERER']);
        exit(); // It's a good practice to exit after redirection
    } else {
        echo "Error: " . mysqli_error($con); // Handle the error appropriately
    }
}
if (isset($_POST['newsletter'])) {
    $email = $_POST['email'];


    $sql = "INSERT INTO `newsletter` (`email`) VALUES ('$email')";
    $res = mysqli_query($con, $sql);
    if ($res) {
        header("Location: " . $_SERVER['HTTP_REFERER']);
        exit(); // It's a good practice to exit after redirection
    } else {
        echo "Error: " . mysqli_error($con); // Handle the error appropriately
    }
}