CODE EXAMPLE FOR PHP

rename image file using post id in wordpress programmatically

function rename_attachment($post_id, $newfilename) {
        $file = get_attached_file($post_id);
        if (!$file) {
            echo "No attachment found!";
            die();
        }
        if (!$newfilename) {
            echo "Filename is empty!";
            die();
        }
        $path = pathinfo($file);
        $newfile = $path['dirname'] . "/" . $newfilename . "." . $path['extension'];
        rename($file, $newfile);
        update_attached_file($post_id, $newfile);

        echo "attachment " . $post_id . " updated from " . $path['basename'] . " to " . $newfilename . "." . $path['extension'];
    }