Check for PHP zip function

The following code assumes zip_open exists, when for many servers it doesn't.

/**
 * hook_link() implementation.
 */
function filebrowser_link($type, $node= NULL, $teaser= FALSE) {
  if ($node->type == 'dir_listing' && !$teaser) {
    $links= array ();
    foreach ($node->file_listing as $file) {
      if ($file['kind'] == 0) {
        $links['file_browser_download_archive']= array (
          'href' => 'filebrowser_download/'.$node->nid.$node->relative_path. ($node->relative_path == '/' ? $node->title : basename($node->relative_path)).".zip",
          'title' => t("Download files as an Archive")
        );
        break;
      }
    }
    return $links;
  }
}

So we don't get a link to download all as a zip, when it isn't possible, please change it to:

/**
 * hook_link() implementation.
 */
function filebrowser_link($type, $node= NULL, $teaser= FALSE) {
  if ($node->type == 'dir_listing' && !$teaser && function_exists('zip_open')) {
    $links= array ();
    foreach ($node->file_listing as $file) {
      if ($file['kind'] == 0) {
        $links['file_browser_download_archive']= array (
          'href' => 'filebrowser_download/'.$node->nid.$node->relative_path. ($node->relative_path == '/' ? $node->title : basename($node->relative_path)).".zip",
          'title' => t("Download files as an Archive")
        );
        break;
      }
    }
    return $links;
  }
}