Are you referring on how to add a Google Adwords Conversion tracking code to your form? If that is the case, I would suggest that you check this guide that my colleague made: http://www.jotform.com/answers/121209-Adding-Adwords-Conversion-Tracking-to-the-Thank-You-page.
If you would like to send POST Data to your custom PHP script, you can do that by following this guide: http://www.jotform.com/help/213-Send-POST-Data-From-JotForm-Using-PHP-in-Custom-Thank-You-Page.
I hope this helps. Do let us know if you need more information on this.