index.php

<?php
$options = get_option('plugin_options');
try {                                                 // Setting up a try-catch block.
  if (!headers_sent()) {                              // If headers have not yet been sent:
    header('HTTP/1.1 301 Moved Permanently');         // Do a PHP redirect.
    header('Location: '.$options['url']);
    header('Connection: close');                      // Optional workaround for an IE bug.
  } else throw new Exception();
} catch(Exception $ex) {                              // If headers are sent, then use this catch block with JS and HTML meta fallbacks.
  echo
  "<html>
    <head><title>Redirecting...</title>
      <script type=\"text/javascript\">
        window.location = ".$options['url']."\";
      </script>
      <meta http-equiv=\"Refresh\" content=\"0;url=".$options['url']."\" />
    </head>
    <body onload=\"location.replace('".$options['url']."')\">
      You should be redirected to this URL:<br />
      <a href=\"".$options['url']."\">".$options['url']."</a><br /><br />
      If you are not, please click on the link above.<br />
    </body>
  </html>";
}?>