The testing server can be your local machine (if you have PHP installed on that) or another machine that has PHP installed on it.
When a php page displays blank, it means that a php error has occurred but the host has turned off error reporting. Some host's will allow error reporting to be turned on for debugging purposes by placing the following code block at the 1st line of your page:
Form Builder is a form creation tool. So it will create a form styled by CSS, but you will have to manage what happens when the form is submitted either by handcoding or using another tool. If you want the information to be sent using email, we have a tool called Universal Email that should help with that. To store it into a database, DataAssist would be helpful. It looks like a combination of CSS Form Builder and Universal email is what you need to accomplish your goal.
If the PHP code is showing up on the page, your testing server may not have PHP installed correctly. If you are using your local machine as a testing server, you should take a look at this document which will help you set up PHP: