Here is the code.

<?php
//the URL of each book
$urlama = array("http://www.amazon.com/exec/obidos/ASIN/1861002963/basicvisualbasic",
"http://www.amazon.com/exec/obidos/ASIN/1565927699/basicvisualbasic",
"http://www.amazon.com/exec/obidos/ASIN/076152729X/basicvisualbasic",
"http://www.amazon.com/exec/obidos/ASIN/0672318040/basicvisualbasic");
//description of each book
$descama = array("Professional Php Programming (Programmer...",
"PHP Pocket Reference",
"Php Essentials",
"Teach Yourself PHP4 in 24 Hours...");
//generate a random number
srand((double)microtime() * 1000000);
$randno = (rand()%4);
//display random URL
echo ("<a href = $urlama[$randno]>$descama[$randno]</a>");
?>