PHP works first time then fails - php

Question

Basically what this does is makes it so after the user presses a button, they have to wait 2 minutes to press it again. When you press it the first time, it works, then if you press it again before 2 minutes, it says "please wait 2 minutes." but after 2 minutes, you can press it as many times as you like without the error, not what I want. Here is the code
<?php
if('sub') {
$client = $_SERVER['REMOTE_ADDR'];
$username="user";
$password="pass";
$database="db";
mysql_connect(localhost,$username,$password);
$time = strtotime("2 minutes");
$now = strtotime("now");
#mysql_select_db($database) or die( "Unable to select database");
$query = "SELECT Time FROM log WHERE IP='$client'";
$result= mysql_query($query);
$num=mysql_num_rows($result);
while($rows=mysql_fetch_array($result)){
$timestamp = $rows['Time'];
}
echo n;
echo $now;
echo t;
echo $timestamp;
if($now < $timestamp)
{
echo "<center><h2 style=\"color:red\" class=\"texts\" id=\"homeLink\">Please wait 2 minutes.</h2></center>";
}
else{
//some other code
$query1 = "INSERT INTO log VALUES ('$client','$time','$username')";
$query2 = "UPDATE `log` SET `Time`='$time' SET `Username`='$username' WHERE `IP`='$client'";
if($num == 0)
{
mysql_query($query1);
}
else
{
mysql_query($query2);
}
mysql_close();
}
?>
As you can see, if there is no row for the IP of the user, it makes a new one, if there is it will update it. After the first time, it no longer works. Hope someone can help. Thanks!

Answer 1

Your update statement is a bit off, so the update fails;
UPDATE `log` SET `Time`='$time' SET `Username`='$username' WHERE `IP`='$client'"
You should only use SET once, like this;
UPDATE `log` SET `Time`='$time', `Username`='$username' WHERE `IP`='$client'"

Answer 2

I'm pretty sure your database does not contain entries you think it contains. Can you check it (IPs and stuff on after button press)?