//in domain2/form.php

//Initialize the Curl session
$ch = curl_init();

//Set curl to return the data instead of printing it to the browser.
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

//Set the URL
curl_setopt($ch, CURLOPT_URL, "http://domain/parse.php");

//Execute the fetch
$data = curl_exec($ch);

//Close the connection
curl_close($ch);

//then you can handle the XML
$xml = new SimpleXMLElement($data);