There must be a better way (to clean a filename)

Pretty much a newbie question... The following lines have been copied from examples I've looked at and are part of a bigger function I am attempting to write, that uploads a file to the server and then does some db work. The purpose of the following lines are to get a 'clean' name for the uploaded file that is then used for other tasks later on. What I mean by 'clean' is that if a user were to upload a file named something silly like "User's Uploaded fiLe.jpg", I'll end up with "user_s_uploaded_file.jpg" The following lines actually return "user_s_uploaded_file_jpg.jpg" which is OK but could be better. I understand what is happening, and I've tried a few variations to the ereg_replace to get it to leave the period alone (so I don't have to put the extension back on) but haven't had any success. Would anyone care to suggest the right expression, or an overall better way I could/should handle something like this? $realname = strtolower($HTTP_POST_FILES['userfile']['name']); $extension = substr(strrchr($realname,"."),1); // remove %20 and the like from name $realname = urldecode($realname); // replace multiple non-word characters with a single "_" $cleanedFilename = ereg_replace("[^[:alnum:]]", "_", $realname); // Get rid of extra underscores $cleanedFilename = ereg_replace("_+", "_", $cleanedFilename); $cleanedFilename = ereg_replace("(^_|_$)", "", $cleanedFilename); // The final name $save_name = "$cleanedFilename"."."."$extension" TIA, verdon