<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>Document</title>
<link href="https://cdnjs.cloudflare.com/ajax/libs/mediaelement/4.0.3/mediaelementplayer.min.css" rel="stylesheet" type="text/css" />
</head>
<body>
<video width="640" height="360">
<source src="http://clips.vorwaerts-gmbh.de/big_buck_bunny.mp4" type="video/mp4">
</video>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/mediaelement/4.0.3/mediaelementplayer.min.js"></script>
<script>
$('video').mediaelementplayer();
</script>
</body>
</html>
<a href="index.php?cat=1">
<a href="index.php?cat=2">
<a href="index.php?cat=3">$id_cat = $_GET['cat']; // сюда попадет id категории предположим цыфра 3
// делаем запрос
// Вывести все из таблице videos где id = 3 ну и сортировка ORDER BY `id` DESC LIMIT 5
$sql = "SELECT * FROM `videos` WHERE id=$id_cat ORDER BY `id` DESC LIMIT 5";
$videos = mysqli_query($connection, $sql);