Webform report error - Call-time pass-by-reference has been deprecated

I am getting a warning message as below when i am creating a webform report using a webform i created

Warning: Call-time pass-by-reference has been deprecated; If you would like to pass it by reference, modify the declaration of [runtime function name](). If you would like to enable call-time pass-by-reference, you can set allow_call_time_pass_reference to true in your INI file in D:\wamp\www\pmo\sites\all\modules\webform_report\webform_report.inc on line 215
Can someone tell me what is this warning message and how it can be rectified.

Thanks