simple file cache and check in php

PHP

/* file cache */
      require_once("lib/simple_html_dom.php");
      $import_url_md5 = md5($import_url);
      $current_working_directory = getcwd();
      $filename = $current_working_directory . "/cache/" . $import_url_md5 . ".html";
      $filename_link = "/cache/" . $import_url_md5 . ".html";

      // cache it... or not...
      $file_cache = true;
      if($file_cache) {
        if(file_exists($filename)) {
          $out .= "using cache file: <a href='$filename_link'>$filename_link</a> <br />";
          $html = file_get_html($filename);
        } else {
          $out .= "added cache file: <a href='$filename_link'>$filename_link</a> <br />";
          $html = file_get_html($import_url);
          // save it for later...
          file_put_contents(
             $filename,
             $html
          );
        }
      } else {
        // no cache
        $out .= "cache disabled<br />";
        $html = file_get_html($import_url);
      }
      // return $out;
      // exit();
      /* file cache */