Where did they go today? Knowing where people leave to and more.

Did you wonder where and how people leave off your site? With php3 it is easy to trace this. Sure, several solutions of redirect-cgi's exist, but why bother with another language when you can keep it straight to php3 and make it more comfortable?

My setting for writing this from scratch was a site where I had multiple pages with identical links in a part of them, but I'd wanted to know the use of the external links in detail: Who left where from which page and when. So here is how it works:

When you read the documentation about php3 in detail, you may have come across this kind of one-liner: <?php Header( "Location: http://www.php.net"); exit; ?> You find it in Section XIV. It uses a HTTP redirect command to make the users browser access a new location. This is a good example how simple things in PHP3 can be: We will expand it, so that we make a suitable tool for the curious ;).

First we make targeting more flexible, it is the 'where'. This one is easy, because you just add a parameter to the URL of the redirector page. I'll call it <?php  '$u_target' ?>. (u_ stands for URI/URL, this is a personal way to determine where the variable belongs to that I am using. Others: db_ is for database , p_ for page , f_ for function and so on.)

Then we want to record from 'which' page the link was activated. Since the referrer-information is sometimes filtered out by proxies, browsers and firewalls, we will use the additional variable <?php  '$u_referrer' ?> for this purpose. You can use simple keywords like 'homepage', the name of the page example.html or the full address "http://...". It doesn't really matter, but keywords are better to understand on first look. When you skip this parameter, <?php $HTTP_REFERER ?> is used automatically. Note that if it doesn't exist either, <?php  '$u_referrer' ?> will be set to 'none'.

We will determine the "who" by using server-variables. We'll take <?php $REMOTE_ADDR ?> address for this purpose, since Apache and IIS deliver it in nearly 90% of all installations ;). <?php $REMOTE_HOST ?> is better but since DNS-lookup is switched off sometimes, you'll have to try out on your server yourself. (Use <?php phpinfo() ?> for this purpose. It's tip I got from Tim and others which lead also to this script. Thanks ;)

'When' is easy: <?php time() ?> is all we need.

Logging the information gathered to a database is the method of choice. Since the data-structure is simple and flat, you should be able to use any kind of solutions - even plain text files will do it. Since MySQL is nice for this job, we'll take it for our purpose.

Since this article focuses on redirecting, I will keep the part of information exchange with the database brief. You'll find more information on this topic here in phpbuilder.com and on the web.

Here is the SQL-Command for creating the table in MySQL:

# Definition
# Table structure for table 'redirect'
#
CREATE TABLE redirect (
  target varchar(80) DEFAULT 'no target' NOT NULL,
  referrer varchar(80) DEFAULT 'none' NOT NULL,
  client varchar(40) DEFAULT 'no client' NOT NULL,
  timeused datetime DEFAULT '0000-00-00 00:00:00' NOT NULL
);

You can easily expand the table for additional parameters like Keyword for the link, User ID's and more. What follows is the code for the php3-Page: redir.php3

<?php
 
// Where did they go today? Version 1.02 - redir.php3
// (c) 1998 by smk%40well.com

// Set variables for Database Access - you'll have to set up your own
    $db_server =  "127.0.0.1";
    $db_user =  "redirector";
    $db_pass =  "secret";
    $db_data =  "redir";
    $db_table =  "redirect";


// First, check target
if (!isset($u_target)) 
    die( "Sorry, no link was set in \$u_target");

// Second, is the referrer set? Note: HTTP_REFERER and some other variables 
//have to be written uppercase or they won't work.

if (!isset($u_referrer)) {
    if (!isset($HTTP_REFERER)) {
        $u_referrer =  "none";
    } else {
        $u_referrer = $HTTP_REFERER;
    };
};

// Now the client address

if (!isset($REMOTE_ADDR)) {
    $p_remotehost =  "no client address";
} else {
    $p_remotehost = $REMOTE_ADDR;
};

// And what time is it now?
$p_timeused = date( "Y-m-d H:i:s",time());

// Get connected and transfer data
@mysql_connect( "$db_server", "$db_user", "$db_pass") or 
    die( "Couldn't connect to the database-server!");
@mysql_select_db( "$db_data") or 
    die( "Can connect to the server, but not to the table or database itself");
@mysql_db_query($db_data ,  "insert into $db_table values('$u_target','$u_referrer',
    '$p_remotehost','$p_timeused')");

// And now she/he's gone with the wind ;)

Header( "Location: $u_target");
exit; 

?>

When you have set up the database and placed the page right you can use it in different ways:

First, you can use it for standard <a href="/old?u=http%3A%2F%2Fwww.phpbuilder.com%2Fcolumns%2Fredir.php3%3Fu_target%3Dhttp%3A%2F%2Fwww.zet.net&y=1999"> -commands. Second, you can use it in special forms for easy (and logged ;) navigation. Look at this example:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

<html>
<head>
    <title>Where did they go today?</title>
</head>
<body>

<form action="/old?u=http%3A%2F%2Fwww.phpbuilder.com%2Fcolumns%2Fredir.php3&y=1999" method="POST" target="">

<select name="u_target" size="1">
    <option value="http://www.slashdot.org">News for Nerds</option>
       <option value="http://www.phpbuilder.com">News for cool Coders</option>
       <option value="http://www.hotbot.com">If you can't find it there...</option>
       <option value="http://community.zet.net">This is my baby...</option>
</select>
<input type="Submit">
</form>

</body>
</html>

Third: If you fear of getting 'copied' away with all of you links on your site, you can expand the script, so that the parameter '$u_refferer' is looked up in a separate database and replaced by an address. (Like the one in html: 1 is for www.slashdot.org, 2 is for www.phpbuilder.com, and so on)

Finally: Mail me an other ideas you have! Tell me if you want this code expanded with user-id's, symbolic names for links and so on. I will put this script on an own webpage soon and if I have the time, I will enhance it.

Sebastian