xlsxwriter.class.php
public static function xmlspecialchars($val)
	{
		//note, badchars does not include \t\n\r (\x09\x0a\x0d)
		static $badchars = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x0b\x0c\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x7f";
		static $goodchars = "                              ";
		return strtr(htmlspecialchars($val, ENT_QUOTES | ENT_XML1), $badchars, $goodchars);//strtr appears to be faster than str_replace
	}
public static function xmlspecialchars($val)
	{
		//note, badchars does not include \t\n\r (\x09\x0a\x0d)
		static $badchars = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x0b\x0c\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f\x7f";
		static $goodchars = "                              ";
		return strtr(htmlspecialchars($val, ENT_QUOTES | ENT_XML1), $badchars, $goodchars);//strtr appears to be faster than str_replace
	}
------------------------------------------------------------------