Abfrage DB max. Wert

<?php

ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);
error_reporting(E_ALL ^ E_NOTICE);

function maxdaytemp(){
    $mysqlhost = "localhost";
    $mysqluser = "andreas";
    $mysqlpwd = "";
    $mysqldb = "wetter";

    $connect = new mysqli($mysqlhost, $mysqluser, $mysqlpwd, $mysqldb) or die ("Could not connect to DB!");

    if (!$connect) {
      die("Connection failed: " . mysqli_connect_error());
    }

    $sql = "SELECT MAX(Temperatur_Balkon) AS maxtemp FROM `temperaturverlauf` ORDER BY Zeit DESC LIMIT 288";
    $result = mysqli_query($connect, $sql);

    $row = mysqli_fetch_array($result);
    echo $row["maxtemp"];
}

?>

<!DOCTYPE html>
<html lang="de" >
<head>
    <meta charset="UTF-8">
    <title>Temperaturverlauf</title>
    <link rel="stylesheet" href="style.css">
</head>
<body>

<div id="maxtemperatur" ><p>Höchste Temperatur der letzten 24 Stunden: <b><?php maxdaytemp() ?></b></p><div>

<div id="mintemperatur" ><p>Niedrigste Temperatur der letzten 24 Stunden: <b></b></p><div>

</div>

</body>
</html>
hi