There are two types of codes we have to set up for tracking affiliates.

The first is called "click.php." This file is called when visitors click a link on an affiliate's website.

<?
  include("common.php");

  if( $_REQUEST['refid'] ){
    $mykey = makeKey(10);
    SetCookie ("affid",$mykey);
    $_SESSION['affid'] = $mykey;
    mysql_query("UPDATE affiliates SET
clicks=clicks+1 WHERE akey='".$_REQUEST['refid']."'",DBH);
    mysql_query("INSERT INTO affstats SET
akey='".$_REQUEST['refid']."',type='1',
OrderID='".$mykey."'",DBH);
  }
  header("Location: $redirecturl");
?>

Now, create a file called "sale.php":

<?
  include("common.php");

  $affid = $_SESSION['affid'];
  if (!$affid){
    $affid = $HTTP_COOKIE_VARS['affid'];
  }
  if (!$affid){
    exit;
  }else{
    mysql_query("UPDATE affstats SET
type='2',price='{$affpay}',paid='0' where OrderID = '{$affid}'",DBH);
  } 
?>

The file sale.php is called by adding it to your site like this:

  <img src="/affiliates/sale.php">

Managing Affiliates

Managing affiliates is important. We need to have a way to manage affiliates so we can set them as being paid, and perform other tasks. For the Affiliate management part, we will create five files.

The first file is "accesscontrol.php." This file is similiar to login.php but works for the management area.

<?php
  session_start();
  $auid = isset($_POST['auid']) ? $_POST['auid'] : $_SESSION['auid'];
  $pwd = isset($_POST['pwd']) ? $_POST['pwd'] :
$_SESSION['pwd'];

  if(!isset($auid)) {
    loginform();
    exit;
  }
  if( $auid != $aduser || $pwd != $adpass ){
    unset($_SESSION['auid']);
    unset($_SESSION['pwd']);
    loginform();
    exit;
  }else if( $auid == $aduser && $pwd ==
$adpass ){
    $_SESSION['auid'] = $auid;
    $_SESSION['pwd'] = $pwd;
  }
?>
<?
  function loginform(){
    global $sitename;
?>
    <CENTER>
    <BR>
    <FONT FACE=verdana color=#FFFFFF
size=5><B><?=$sitename?> Login</B></FONT>
    <BR>
    <TABLE cellspacing=0>
    <FORM method=post>
    <TR><TD>Username:
      <TD><INPUT type=text name=auid size=16>
    <TR><TD>Pass:
      <TD><INPUT type=pass name=pwd size=16>
    <TR><TD colspan=2><INPUT type=submit
value="Log In >>"></TD>
    </FORM>
    </TABLE>
    <BR>
<?
  }
?>

Now, we create "manage.php":

<?
  include("common.php");
  include("accesscontrol.php");
  include("header.php");
  $mode = isset($_REQUEST['mode']) ? $_REQUEST
['mode'] : '';
  switch($mode){
    case "stats":
      include("managestats.php");
      break;
    case "payout":
      include("payout.php");
      break;
    default:
      include("managemain.php");
      break;
  }
?>

<?
  include("footer.php");
?>

Next, we do "managemain.php":

<p>Here are your affiliates, click on a username to view their stats.</p>
<table border=1>
<tr>
  <td>Username</td>
  <td>Password</td>
  <td>Email</td>
  <td>Affiliate Key</td>
<?
  $results = mysql_query("SELECT *  FROM
affiliates ORDER BY username;",DBH);
  while( $row = mysql_fetch_assoc($results) ){
    echo "<tr>";
    echo "<td><a href='manage.php?mode=stats&userId={$row['ID']}'>{$row
['username']}</a></td>";
    echo "<td>{$row['password']}</td>";
    echo "<td>{$row['email']}</td>";
    echo "<td>{$row['akey']}</td>";
    echo "</tr>";
  }
?>
</table>

The next file will be "managestats.php":

<?
  $mystats = AffiliateStats($_GET['userId']);
  if($mystats['clicks'] > 0){
    $ratio = number_format( (($mystats
['orders'] / $mystats['clicks']) * 100), 2 )." %";
  }else{
    $ratio = "0 %";
  }
?>
<b>Stats</b><br/>
<table align=center width=350 border=1>
<tr>
  <td>Total Clicks:</td>
  <td><?=number_format($mystats['clicks'],0)?>&nbsp;</td>
</tr>
<tr>
  <td>Total Orders:</td>
  <td><?=number_format($mystats['orders'],0)?>&nbsp;</td>
</tr>
<tr>
  <td>Ratio %:</td>
  <td><?=$ratio?>&nbsp;</td>
</tr>
</table>
<br>
<table align=center width=350 border=1>
<tr>
  <td>Amount Earned:</td>
  <td>$<?=number_format($mystats['order_total'],2)?></td>
</tr>
<tr>
  <td>Payments Pending:</td>
  <td>$<?=number_format($mystats['pending_total'],2)?></td>
</tr>
<tr>
  <td>Amount Paid:</td>
  <td>$<?=number_format($mystats['paid_total'],2)?></td>
</tr>
</table>
<?
  echo "<div align='center'><a
href='manage.php?mode=payout&userId={$_GET
['userId']}'>Manage Payments</a></div>";
?>

And finally, we create "payout.php":

<?
  if($_GET['setaspaid']){
    mysql_query("UPDATE affstats SET paid='1'
WHERE ID='{$_GET['setaspaid']}'",DBH);
  }
  if($_GET['setasunpaid']){
    mysql_query("UPDATE affstats SET paid='0'
WHERE ID='{$_GET['setasunpaid']}'");
  }
  $sql = "SELECT * FROM affiliates WHERE
ID='{$_GET['userId']}'";
  $lo = mysql_query( $sql );
  $affi = mysql_fetch_assoc($lo);
?>
<?      if($affi['ptype']){       ?>
Requested Payment Method: <?=( strtolower($affi
['ptype']) == "paypal" ? "PayPal" : "Check")?
><br>
<?      }       ?>
Payment Account: <?=( strtolower($affi
['ptype']) == "paypal" ? $affi['pemail'] :
nl2br($affi['address']) )?><br>
<br>
<table align=center width=350 border=1>
<?
  $q1 = "select * from affstats WHERE akey=
'{$affi['akey']}' AND type=2 GROUP BY OrderID";
  $r1 = mysql_query($q1,DBH) or die(mysql_error());
  while($a1 = mysql_fetch_assoc($r1)){
?>
    <tr>
      <td>Amount Earned:</td>
      <td>$<?=$a1['price']?></td>
<?                      if($a1[paid] == 1){     ?>
      <td><a href="manage.php?
mode=payout&userId=<?=$_GET['userId']?
>&setasunpaid=<?=$a1['ID']?>">Set As Not
Paid</a></td>
<?                      }else{  ?>
      <td><a href="manage.php?
mode=payout&userId=<?=$_GET['userId']?
>&setaspaid=<?=$a1['ID']?>">Set As
Paid</a></td>
<?                      }       ?>
    </tr>
<?
  }
?>
</table>

Paying Your Affiliates

I've given you an interface to use to see how much affiliates have made and set those earnings to paid, but you still have to pay them using the method they specify. If affiliates ask to be paid via check, then send them a check.

One good practice is to set a minimum payment level, so that affiliates only get paid when they reach $20.00 or something like that.

In Conclusion

So, you now have a basic affiliate system. This can be made more complicated by modifying the code to allow banners, add more payout options, and so on. But I was aiming to give you something more simple to work with as a start.

Affiliate systems can be very complex sometimes and this article was intended to give you a system that wasn't complex at all.