HubSpot GoToWebinar Double Post from a form (not a HS landing page)

hubspot_gtw_double_post.php

<?php

if ($_SERVER['REQUEST_METHOD'] == "GET") {
   header('Location:http://thefreshdish.com');

   $gtwPost = "";
   //Create string for GoToWebinar from same form POST data
   $gtwPost = "WebinarKey=" . urlencode($_GET['WebinarKey'])
     . "&Form=" . urlencode($_GET['Form'])
     . "&Name_First=" . urlencode($_GET['firstName'])
     . "&Name_Last=" . urlencode($_GET['lastName'])
     . "&Email=" . urlencode($_GET['email']);
   //Set POST URL for GoToWebinar
   $gtw_url = "https://www1.gotomeeting.com/en_US/island/webinar/registration.flow";
   //Start GoToWebinar submission
   $curl = @curl_init();
   @curl_setopt($curl, CURLOPT_POSTFIELDS, $gtwPost);
   @curl_setopt($curl, CURLOPT_URL, $gtw_url);
   @curl_setopt($curl, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_0);    
   @curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
   @curl_exec($curl);
   $info = @curl_getinfo($curl);
   @curl_close($curl);
   //End GoToWebinar registrant submission

   //START HubSpot Lead Submission
   $strPost = "";
   //create string for HubSpot with form POST data
   $strPost = "FirstName=" . urlencode($_GET['firstName'])
     . "&LastName=" . urlencode($_GET['lastName'])
     . "&Email=" . urlencode($_GET['email'])
     . "&IPAddress=" . urlencode($_SERVER['REMOTE_ADDR'])
     . "&UserToken=" . urlencode($_COOKIE['hubspotutk']);
   //set POST URL for HubSpot
   $hubspot_url = "http://amott.app5.hubspot.com/?app=leaddirector&FormName=GTW+Process";
   //intialize cURL and send POST data
   $ch = @curl_init();
   @curl_setopt($ch, CURLOPT_POSTFIELDS, $strPost);
   @curl_setopt($ch, CURLOPT_URL, $hubspot_url);
   @curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
   @curl_exec($ch);
   @curl_close($ch);
   //END HubSpot Lead Submission
}

?>

hubspot_gtw_form.html

<form method="get" action="http://<path-to-file>/gtw-process.php">
   First Name: <input name="firstName" size="40" type="text" />
   Last Name: <input name="lastName" size="40" type="text" />
   Email: <input name="email" size="40" type="text" />
   <input name="WebinarKey" type="hidden" value='<ENTER WEBINAR KEY HERE>' />
   <input name="Form" type="hidden" value="webinarRegistrationForm" />
   <input name="Template" type="hidden" value="https://www1.gotomeeting.com/en_US/island/webinar/registration.tmpl" />
   <input type="submit" value="Submit" />
</form>

Pardon the stupid question... How exactly does this know where to post the info to hubspot? I guess I'm referring to how does it know what hubspot account to post the info to?

Is it based off of the url to the hubspot form?