Letzes Vorkommen eines Zeichen ermitteln .... Wie?

[Calocybe]

Hallo Frank!

substr($url,rindex($url,"/")+1)= "f_".substr($url,rindex($url,"/")+1);

Optimized:  
    substr($url, rindex($url, "/"), 1) = "/f_";
(untested)

So long