You could use cookies toolkit to help make this work.
The problem is the way forms work:
When a form submits, posted information is available as long as the forms action page is precessing. Once the forms action page is through processing, the post collection is cleared.
What you are trying to do is to have the form post to itself to store the information in a database, then redirect to another page to process the information again. This cant be done without reposing the form since the post is cleared when it redirects.
So to get around this, apply the Store Entire Form in cookie behavior from cookies toolkit to the onSubmit event of the form.
Create another page with the exact same form on it, all of the form elements must have the exact same name. Set the Insert Record behavior to redirect to this page, then apply set entire form from cookie behavior to the onLoad event of the body tag. Set the forms action to post to the Icontact PHP page.
You can then add the Call Javascript Behavior to the onLoad event of the body tag and set it to:
document.getElementById('<form ID>').submit();