set_error_handler() UNDEFINED?

I don't understand how to use the set_error_handler() funciton. I'm testing it with the script listed below from Zend.com. Here's the link: http://www.zend.com/zend/art/mistake1.php#Heading10 If I set error_reporting(15) (or anything greater than 0, in fact), I get the following error: error Fatal error: Call to undefined function: set_error_handler() in ... If I lower the error_reporting(0), I don't get the fatal error, but I get an empty HTML document: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=iso-8859-1"></HEAD> <BODY></BODY></HTML> In no case does the file error_file, with permissions 777, ever get written to. Can you shed any light on my confusions? Thank you, Ted <?php // void error_handler(string type, string message, string file, int line) // Custom error handler, set by the set_error_handler() // function. // function error_handler ($type, $message, $file=__FILE__, $line=__LINE__) { error_log("$message, $file, $line", 3, 'error_file'); if ($type & E_ERROR) { print 'An error occurred, it has been logged and it will be addressed.'; exit; } } set_error_handler('error_handler'); ?>