Check MySQL queries per second periodically from PHP

mysqlqps.php

<?php

$mysqli = new mysqli("db", "user", "pass", "db");

/* check connection */
if ($mysqli->connect_errno) {
    printf("Connect failed: %s\n", $mysqli->connect_error);
    exit();
}

while (true)
{
    $results = $mysqli->query("show global status like 'Questions'")->fetch_array();
    $questions_1 = $results[1] - 2;

    $results = $mysqli->query("show global status like 'Uptime'")->fetch_array();
    $uptime_1 = $results[1];

    sleep(3);

    $results = $mysqli->query("show global status like 'Questions'")->fetch_array();
    $questions_2 = $results[1] - 2;

    $results = $mysqli->query("show global status like 'Uptime'")->fetch_array();
    $uptime_2 = $results[1];


    echo "Q1:", $questions_1, "\n";
    echo "U1:", $uptime_1, "\n";

    echo "Q2:", $questions_2, "\n";
    echo "U2:", $uptime_2, "\n";

    echo "QPS:", ($questions_2-$questions_1)/($uptime_2-$uptime_1), "\n\n";
}