amazon link regex help

[the_sisko]

Hi guys,

I'm trying to replace a normal amazon.de Link oder any amazon.de Link with a affiliate ID to my own:

http://www.amazon.de/exec/obidos/ASI...904298-7328563

-->

http://www.amazon.de/exec/obidos/ASI...G/chemieonline

I wrote a function for it but have some probs. There must be a whitespace at the endling of the string. otherwise if the url is the last thing in the string it won't work... I added an extra whitespace at the end in the funktion.
Also if the link ends like http://www.amazon.de/exec/obidos/ASI...904298-7328563[ /url ] the [ /url ] get cut of...

Need a little help as I'm not that regex guy:

PHP Code:

<?
//replace function
function cdk_a($string,$id="chemieonline") {
    $string .= " ";
    return  preg_replace("/(http:\/\/|http:\/\/www.|www.|)amazon.de\/exec\/obidos\/ASIN\/([A-Z0-9]+)([^\"\n]*?)\s+/i","http://www.amazon.de/exec/obidos/ASIN/$2/$id ",$string);
}

//test urls
$url ="Schreiben wir einen kleinen Text mit einer Url zu Amazon mit allen Werten: 
        [url]http://www.amazon.de/exec/obidos/ASIN/B0001RTYDG/ref=amb_center-4_113630_1/028-9904298-7328563[/url] ,
        dann lassen wir das www weg: [url]http://amazon.de/exec/obidos/ASIN/B0001RTYDG/ref=amb_center-4_113630_1/028-9904298-7328563[/url] ,
        oder auch einfach das http: [url]www.amazon.de/exec/obidos/ASIN/B0001RTYDG/ref=amb_center-4_113630_1/028-9904298-7328563[/url] ,
        und zum Schlu? einfach beides: amazon.de/exec/obidos/ASIN/B0001RTYDG/ref=amb_center-4_113630_1/028-9904298-7328563";
              
//do replace
    $ausgabe = cdk_a($url);
          

//ausgabe
echo "<blockquote>";
print($url);
echo "</blockquote>\n";
echo "<blockquote>";
print($ausgabe);
echo "</blockquote>";
             

?>