Can anybody please help me with a script

I am running an image site.I need a script that can change the ad after each page refresh.I mean i am running 3 ad services.if 1 ad service is displayed in one page view,next time when the same user views the page,the ad displayed should be the ad from another service.Is that possible?Can anyone provide me with a working script for that?

 

I wrote a little script based on cookies for You.
The code is pretty self-explaining.

<?php
  $ad_mem = "ad_1"; // First time ad_1, if no cookie is set
  if (isset($_COOKIE['ad_mem']))
    $ad_mem = $_COOKIE['ad_mem']; // Else use cookie value

  if ($ad_mem == 'ad_1')
  {
  	// Show ad 1
    echo "<a href=\"#\"><img src=\"img/img_ad_1.jpg\" alt=\"Advertisement 1\" title=\"Advertisement 1\"></a>";
  	// Change to 2 advertisement for next time
  	setcookie("ad_mem", "ad_2");
  }
  if ($ad_mem == 'ad_2')
  {
  	// Show ad 2
    echo "<a href=\"#\"><img src=\"img/img_ad_2.jpg\" alt=\"Advertisement 2\" title=\"Advertisement 2\"></a>";
  	// Change to 3 advertisement for next time
  	setcookie("ad_mem", "ad_3");
  }
  if ($ad_mem == 'ad_3')
  {
  	// Show ad 3
    echo "<a href=\"#\"><img src=\"img/img_ad_3.jpg\" alt=\"Advertisement 3\" title=\"Advertisement 3\"></a>";
  	// Change back to 1 advertisement for next time
  	setcookie("ad_mem", "ad_1");
  }
?>

Code (markup):

Enjoy!