Showing a different "Back to XXX" depending on what page a user comes from?

<?php
// swapChunkonReferer v 0.1
// Snippet by killorbytes
// 3/4/07

//chunkOne is the Chunk to be displayed of the string search of the referer is true
//chunkTwo is the Chunk to display if the string search does not find a match
//refererID is the search string to match against the referer

/* Example Call

[!swapChunkonReferer? &chunkOne=`nameofFirstChunk` &chunkTwo=`nameofSecondChunk` &refererID=`referingDocumentAlias`!]

*/

$chunkOne = isset($chunkOne) ? $chunkOne : 'back2caseStudies'; //Set name or use default
$chunkTwo = isset($chunkTwo) ? $chunkTwo : 'destinationChunk'; //Set name or use default
$refererID = isset($refererID) ? $refererID : 'case-studies'; //Set name or use default
$referer = $_SERVER['HTTP_REFERER'];

if(stristr($referer,$refererID)) {
echo '{{' . $chunkOne . '}}';
} else {
echo '{{' . $chunkTwo . '}}';
}
?>