500 PHP error

/home/mnl/public_html/shopeo/protected/site/controllers/

OrderController.php line 138 Optional parameter $k1 declared before required parameter $id is implicitly treated as a required parameter

Stack trace
#1 /home/mnl/public_html/shopeo/yii/framework/web/CWebApplication.php ::require (354)
#2 /home/mnl/public_html/shopeo/yii/framework/web/CWebApplication.php CWebApplication::createController (276)
#3 /home/mnl/public_html/shopeo/yii/framework/web/CWebApplication.php CWebApplication::runController (141)
#4 /home/mnl/public_html/shopeo/yii/framework/base/CApplication.php CWebApplication::processRequest (185)
#5 /home/mnl/public_html/shopeo/index.php CApplication::run (159)