Html/php hard refresh

Question

I am trying to hard-refresh my page, since I randomize the order of my database, but when I refresh the page via the html button it doesn't work, until a bit of time has passed. I assume it is due to the web-browser's cache. it also doesn't work if I refresh it via f5, but if I use shift+f5 it works.

<?php
if(isset($_GET["genre"])) {
$db = mysqli_connect("localhost","localhost","","test","3306");
$genre = $_GET["genre"];
$sql = "SELECT tittel, aar, id, genre, plot FROM gruppe3_film WHERE genre LIKE '%$genre%' ORDER BY RAND()";
$resultat = mysqli_query($db, $sql);

$rad = mysqli_fetch_assoc($resultat);
    $tittel = $rad['tittel'];
    $aar = $rad['aar'];
    $id = $rad['id'];
    $plot = $rad['plot'];
    echo "
   <h2>$tittel ($aar)</h2>
   <br><a href='javascript:location.reload();'><img src='../image/DBFilmCover/$id.jpg'></a>
   <h4>$plot</h4>
   <hr><button><a href='javascript:location.reload();'><div class='black'>New Random $genre Movie</div></a></button>";
?>

As you see I currently use <a href='javascript:location.reload();'>, but I have also tried javascript:window.location.href=window.location.href inside href

Answer 1

Using html4

<meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate" />
<meta http-equiv="Pragma" content="no-cache" />
<meta http-equiv="Expires" content="0" />

Using php

header("Cache-Control: no-cache, no-store, must-revalidate"); // HTTP 1.1.
header("Pragma: no-cache"); // HTTP 1.0.
header("Expires: 0");