tFPDF::_checkoutput PHP Method

    function _checkoutput()
    {
        if (PHP_SAPI != 'cli') {
            if (headers_sent($file, $line)) {
                $this->Error("Some data has already been output, can't send PDF file (output started at {$file}:{$line})");
            }
        }
        if (ob_get_length()) {
            // The output buffer is not empty
            if (preg_match('/^(\\xEF\\xBB\\xBF)?\\s*$/', ob_get_contents())) {
                // It contains only a UTF-8 BOM and/or whitespace, let's clean it
                ob_clean();
            } else {
                $this->Error("Some data has already been output, can't send PDF file");
            }
        }
    }