[PHP] Hope any body can fix this!!!

[Radwan Aladdin]

Hi..

I made the following PHP script.. And every time I try it, it shows an error 
message... I think there is a wrong with ($LogoutTime - $RightLoginTime'). So please 
try to fix the error..

What I want to do is to insert a logout time and if  (LogoutTime - LoginTime = 20) for 
example.. then make the field "LessonNumber" = "Its value + 1" (2 + 1 = 3 for example)

This is the script :-

<?php

include("Config.php");

$link = mysql_connect("$user_hostname", "$user_username", "$user_password");
mysql_select_db("$user_database", $link);

$UserName = $_GET['UserName'];
$Password = $_GET['Password'];
$LogoutTime = date("U");

$query1 = "UPDATE accounts SET LogoutTime=$LogoutTime";
$query2 = "SELECT LoginTime,Distance,LessonNumber FROM accounts WHERE 
UserName='$UserName' AND Password='$Password'";
$query3 = "UPDATE accounts SET LessonNumber=LessonNumber + 1";
$result = mysql_query($query1) or die("Query error: " . mysql_error());


$RightLoginTime = 'LoginTime';
$Distance = 'Distance';
$LessonNumber = 'LessonNumber';
$LessonsTimeLimit = "30";

$query4 = "INSERT INTO accounts (Distance) ('$LogoutTime - $RightLoginTime')";
$result2 = mysql_query($query4) or die("Query error: " . mysql_error());

if($Distance == $LessonsTimeLimit){
    $result3 = mysql_query($query3) or die("Query error: " . mysql_error());
}else{
    echo "Not yet!";
}

?>

Waiting your replies..

Best regards..