constants STDOUT, STDERR, STDIN not working in 5.2.x?

Hello, I found different code examples like this, which use the file handle STDERR just like this: <?php fwrite(STDERR, "hello\n"); ?> Also, the PHP documentation of input/output streams (http://php.net/manual/de/wrappers.php.php) says: "It is recommended that you simply use the constants STDIN, STDOUT and STDERR instead of manually opening streams using these wrappers." I don't want to use the "php://stderr" wrapper, because this just creates a duplicate of the original STDERR handler and if I'm closing "php://stderr", the original STDERR still would exist. When I'm using this code, I only get: <b>Notice</b>: Use of undefined constant STDERR - assumed 'STDERR' in <b>/test.php</b> on line <b>4</b><br /> <br /> <b>Warning</b>: fwrite(): supplied argument is not a valid stream resource in <b>/test.php</b> on line <b>4</b><br /> How can I access the original STDERR handle? The constant should be there, but does not exist. regards Marten