live visitor counter for single page - php

Question

I'm current working on a live leader-board page and i am trying to add a live view counter to it. I am not getting and data sent to the database and its not reading from the database. I have checked the db connection and its working. I have checked the code in php tester and it has no errors.
Take a look and let me know what i missed, Thanks
class VisitorCounterReal {
var $sessionTimeInMin = 5; // time session will live, in minutes
function VisitorCounter() {
$ip = $_SERVER['REMOTE_ADDR'];
$this->cleanVisitors();
if ($this->visitorExists($ip))
{
$this->updateVisitor($ip);
} else
{
$this->addVisitor($ip);
}
}
function visitorExists($ip) {
$query = "SELECT * FROM counter WHERE ip = '$ip'";
$res = mysqli_query($connection, $query);
if (mysqli_num_rows($res) > 0)
{
return true;
} else
if (mysqli_num_rows($res) == 0)
{
return false;
}
}
function cleanVisitors()
{
$sessionTime = 30;
$query = "SELECT * FROM counter";
$res = mysqli_query($connection, $query);
while ($row = mysqli_fetch_array($res))
{
if (time() - $row['lastvisit'] >= $this->sessionTimeInMin * 60)
{
$dsql = "delete from counter where id = $row[id]";
mysqli_query($dsql);
}
}
}
function updateVisitor($ip)
{
$query = "UPDATE counter SET lastvisit = '" . time() . "' WHERE ip =
'$ip'";
mysqli_query($connection, $query);
}
function addVisitor($ip)
{
$query = "INSERT INTO counter(ip, lastvisit) ";
$query .= "VALUES('$ip', '" . time() . "') ";
mysqli_query($connection, $query);
}
function getAmountVisitors()
{
$query = "SELECT COUNT(id) FROM counter";
$res = mysqli_query($connection, $query);
$row = mysqli_fetch_row($res);
return $row[0];
}
function show()
{
echo '<h3>There is ' . $this->getAmountVisitors() . ' watching
online</h3>';
}
}
This is on the live leaderboard page below
<?php
$counter = new VisitorCounterReal; // make a new counter
//content here
$counter->show(); // show the counter
// and here
?>