Query String Data Capture

Dear Friends,

I have followed the tutorial as mentioned in the following tutorial,

How to Capture Referring Sources to Landing Pages and in Forms using Query Strings

Still, I am not able to capture the source data in Hidden Field.

My link looks like this,

http://website.com?source=LinkedIn

I wanted, when we view the Form Submission Data, LinkedIn should be present in the Hidden Field.

Please help me out on this.

Thanks.