class.upload.php is a powerful and mature PHP class to manage uploaded files, and manipulate images in many ways. The script is available under a GPL license.
more info about the class
$this->file_dst_name_body = strtr($this->file_dst_name_body, 'ŠŽšžŸÀÁÂÃÄÅÇÈÉÊËÌÍÎÏÑÒÓÔÕÖØÙÚÛÜÝàáâãäåçèéêëìíîïñòóôõöøùúûüýÿ', 'SZszYAAAAAACEEEEIIIINOOOOOOUUUUYaaaaaaceeeeiiiinoooooouuuuyy');
$this->file_dst_name_body = preg_replace(array('/\s/', '/\.[\.]+/', '/[^\w_\.\-]/'), array('_', '.', ''), $this->file_dst_name_body);
After changing the order of the replacements, putting
at first, the file name is okay. But I don't know about any side effects.