How to return a 404 response?

Question

PHP

Tell me how to give a 404 page correctly
. I have a template in which I determine by GET request whether there is an entry in the database and if so, then I show the page.

if (isset($_GET['shop'])) {
    $offer = isset($_GET['shop']) ? str_replace(" ", "", $_GET['shop']) : null;
    $sql = "SELECT * FROM shops WHERE link_shop = '".$offer."' ";
    $result = mysqli_query($linkMain,$sql);
}

That is, if the user enters the URL /view/?shop=mvideo.ru, the page will be found.
But it will also find it if the user enters something like /view/?shop=mvideo.ru1, etc.

I tried to wrap the page output in a condition that if the string is found, then we show the page, otherwise we return to the working page , redirect to 404 or immediately give the titleheader("HTTP/1.0 404 Not Found");

if (mysqli_num_rows($result) > 0) {

} else {
    
    // header("Location: /view/?shop=mvideo.ru");
// header("HTTP/1.0 404 Not Found");
    header("Location: /404/");
}

What is the right thing to do here so that the search engines respond adequately?

Answer 1

header for search engines will be enough.