switch ($_GET['page']) //this sets up a switch statement, checking for various options. In this case, it gets the value of the "page" variable from the url (filename.php?page=2). If it is "2" it does the code within the "case 2:" block
{     
    case 2: 

    if(isset($_GET["sign"])) //checks if "sign" is set in the url, and gets the value using $_GET[] (if "sign" is set in the url, it will look something like this: filename.php?sign=value)
    {
        //sets the message variable to the value of the "message" field in the form. htmlspecialchars() and addslashes() are both functions that are intended to help protect against hacking or invalid inputs
        $message = htmlspecialchars(addslashes("$_POST[message]"));
        
        //sets the time variable to the current time, in the specified format
        $time = date("F j, Y, g:i a");
        
        //this is a mysql query that saves the data captured within the form to the database
        $querty = mysql_query("INSERT INTO guestbook(owner,postedby,post,time) VALUES('$req_user','$session->username','$message','$time')");

        //displays a message to the user letting him/her know that the comment has been posted.
        echo "<center>Your message has been posted</center><br>"; 
    }
    else
    // if the "sign" variable is not set in the URL, show an error 
    {
        echo ( "Message was not posted" ); // or no request sent
    } 

    // end the switch statement
    break;

}

//sets the req_user variable based on the URL
$req_user = trim($_GET['user']);

// this is a mysql query that gets the comments from the database
$getcomments = mysql_query( "SELECT * FROM `guestbook` WHERE `owner` = '$req_user' ORDER BY `ID` DESC" );

// this loops through all of the results, repeating the code within the loop until there are no more results 
while ($comments = mysql_fetch_array($getcomments))
{
    // this displays the comment from the database
    echo "<a href='userinfo.php?user=$comments[postedby]'>$comments[postedby]</a> ($comments[time]) - $comments[post] <br>";
}

//displays header text
echo "<center><br/><b>Sign $req_user's guestbook</b><br/>

// sets up a form
<form  action='userinfo.php?page=2&user=$req_user&sign=$req_user&from=".$session->username."/' method='POST'>

<textarea name='message' rows='5' cols='30' align='left'></textarea><br/><input type='submit' value='Update' name='submit'></form></center>";

/* Link back to main */
echo "<br>Back To [<a href=\"main.php\">Main</a>]<br>";