Before I link to the external site, I want to send an e-mail containing the form fields to, let's say, firstname.lastname@example.org. I don't want to use mailto: because I don't want to confuse the user by having a mail window appear, so unless I've overlooked something, I need to use PHP mail. I have tested this and it works for me but I don't know how to get the field values to PHP.
I can create a form that sends data to PHP, but when the user submits the form, the validation and the link to the external site are bypassed.
Here is what I want to do when the user clicks "Sign me up":
1. Validate the fields (the same as lines 23 to 39 are doing now).
2. Send the field values via PHP mail.
3. Submit the field contents to the external site (the same as lines 40 and 41 are doing now).