PHP Fatal Error

Hey there,

I had a look at my PHP 5.4 Error log file today and she said:

PHP Fatal error: Undefined class constant ‘HTML_ENCODING_QUOTE_STYLE’ in /is/htdocs/xxx_XXX/www/xx/wp-content/plugins/wp-power-stats/wp-power-stats.php on line 1073, referer: http://…

What exactly am I looking at here? On the PHP 5.3 error log file it doesn’t show that.

https://ww.wp.xz.cn/plugins/wp-power-stats/