prefill forms with httlp post

If I understood you correctly, you want to prepopuilate your form. To achieve that you can use our prepopulate app: http://prepopulate.jotform.io/ 

You can also check this guide: http://www.jotform.com/help/71-Prepopulating-fields-to-your-JotForm-via-URL-parameters 

Hope this will help. Let us know if you need further assistance.