How to determine wether ob_start(); has been called already

Question

I use output buffering for gzip compression and access to what was put out before in a PHP script:

if(!ob_start(\"ob_gzhandler\")) ob_start();

Answer 1

General:

if (ob_get_status())  {
  // ob started
}

More specific

$status = ob_get_status();
if ($status['name']=='ob_gzhandler') {
 // ob named ob_gzhandler started
}