JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
If you want to pass input data form one field to another, why do you want to do that using POST data. You may like to take advantage of our "URL Parameter" feature to achieve your requirement. Please take a look at the following thread where I have explained this in step by step: http://www.jotform.com/answers/396268
If you still want to populate your second form using POST data, you may like to check the following guide for another step by step guide on how to populate your form fields with the value of another form field using POST method: https://www.jotform.com/help/213-Send-POST-Data-From-JotForm-Using-PHP-in-Custom-Thank-You-Page
Do try it out and get back to us if you have any questions.