KCfinder upload image for many users - php

Question

My website lets logged users to use CKeditor and CKFinder to create pages or blog and of course upload image from editor. I got problem for many users that will use the same images in a single folder. I have searching for the same problem on StackOverflow and I found this question:
KCFinder with CKEditor - setting up dynamic folders for upload files.
I think the solution was good, but rather than creating many folders, I am just thinking how to save every user images by using a prefix of their user ID. For example the user with ID 10 will save his images with prefix 10_xxxxx.jpg and so on.
How to do it. Any body could show me where part of the file script that could be modified? I am using KCFinder V.3.12. Sorry for my English.
$_SESSION['id'] = 10;
public function upload() {
$config = &$this->config;
$file = &$this->file;
$url = $message = "";
if ($config['disabled'] || !$config['access']['files']['upload']) {
if (isset($file['tmp_name'])) #unlink($file['tmp_name']);
$message = $this->label("You don't have permissions to upload files.");
} elseif (true === ($message = $this->checkUploadedFile())) {
$message = "";
$dir = "{$this->typeDir}/";
if (isset($_GET['dir']) &&
(false !== ($gdir = $this->checkInputDir($_GET['dir'])))
) {
$udir = path::normalize("$dir$gdir");
if (substr($udir, 0, strlen($dir)) !== $dir)
$message = $this->label("Unknown error.");
else {
$l = strlen($dir);
$dir = "$udir/";
$udir = substr($udir, $l);
}
}
if (!strlen($message)) {
if (!is_dir(path::normalize($dir)))
#mkdir(path::normalize($dir), $this->config['dirPerms'], true);
$filename = $this->normalizeFilename($file['name']);
$target = file::getInexistantFilename($dir . $filename);
if (!#move_uploaded_file($file['tmp_name'], $target) &&
!#rename($file['tmp_name'], $target) &&
!#copy($file['tmp_name'], $target)
)
$message = $this->label("Cannot move uploaded file to target folder.");
else {
if (function_exists('chmod'))
#chmod($target, $this->config['filePerms']);
$this->makeThumb($target);
$url = $this->typeURL;
if (isset($udir)) $url .= "/$udir";
$url .= "/" . basename($target);
if (preg_match('/^([a-z]+)\:\/\/([^\/^\:]+)(\:(\d+))?\/(.+)$/', $url, $patt)) {
list($unused, $protocol, $domain, $unused, $port, $path) = $patt;
$base = "$protocol://$domain" . (strlen($port) ? ":$port" : "") . "/";
$url = $base . path::urlPathEncode($path);
} else
$url = path::urlPathEncode($url);
}
}
}