Be very careful using this function - it's a per-process setting.
If your server is set up to reuse a single PHP process for multiple requests, that means the last setting of this function in any script will affect all other scripts using mysqli.
To be safe always call <? mysqli_report(MYSQLI_REPORT_OFF) ?> at the end of a script. The CGI version of PHP is probably safe from this.
(Tested using PHP 5.0.5, Apache 2 SAPI module)