This module adds the ability to execute arbitrary PHP code when a Webform is validated or submitted. This is intended to replace the existing functionality that was provided in previous versions of Webform that are no longer available in the 3.0 version. This module is not necessary if you are using previous versions of Webform.
This module is extremely dangerous and you should not use it. By using this module you enable any user with the "use PHP for additional processing" permission to wreck absolute havoc on your site, deleting files or dropping your entire database. Generally speaking, even having the ability to enter PHP code into a textarea is a dangerous and ill-advised idea.
Instead, you should be writing code in a module, at the very least, this module serves as a good example of how you can write your own custom module and add any extra code you may want to execute.
If looking to add validation to your form, Webform Validation can solve a lot of situations in a safe manner.
No support is provided on how to write your own custom routines. See the Webform handbook pages for information on how you can use these fields:
Webform (3.x versions)
This project is Abandoned. Use of this module is highly discouraged, not because it is abandoned but because it is highly dangerous. There will not be a Drupal 7 version.