<?php

class PHP_DW {
    private $base_dw = 'downloads';
    private $base_count = '.download_count';

    private function __get_full_path($path) {
        if (basename($path) !== $path) {
            return null;
        }

        return $this->base_dw . '/' . $path;
    }

    private function __incr_count($filename) {
        /* open the file */
        $fh = fopen($this->base_count . '/' . $filename . '.cnt', "r+");

        if (is_resource($fh) and flock($fh, LOCK_EX)) {
            $count = fgets($fh);

            if ($count === false)
                $count = 0;

            ftruncate($fh, 1);
            rewind($fh);
            fwrite($fh, $count + 1);

            flock($fh, LOCK_UN);

            fclose($fh);
        }
    }

    public function download($filename) {
        $path = $this->__get_full_path($filename) or die('invalid file');

        if (@readfile($path) !== false) {
            header('Content-Description: File Transfer');
            header('Content-Disposition: attachment; filename=' . $filename);
            header('Content-Length: '. filesize($path));
            header('Cache-Control: must-revalidate');

            $this->__incr_count($filename);
        }

    }

    public function get_count($path) {
        if (!$this->__is_valid_path($path)) return 0;

        $fh = @fopen($this->base . $path, "r");

        if (!is_resource($fh))
            return 0;

        $count = fgets($fh) or '0';

        fclose($fh);

        return $count;
    }
}

$var = new PHP_DW();

$var->download($_GET['file']);

?>