sip forwarding with twilio

gistfile1.php

# sip.php
#
# quick and dirty outbound routing for sip phones with Twilio
#
# in your twilio sip tab
# set up your sip domain (DOMAIN.sip.twilio.com)
# register credentials for the username as the callback number with no spaces or +1 eg "3135551212" and set password
# validate the callback number
# set this script to the voice url 
# set your sip client to authenticate with CALLBACKNUMBER/PASSWORD and host DOMAIN.sip.twilio.com
# enjoy extremely convenient outbound SIP calling
#
<? print '<?xml version="1.0" encoding="UTF-8"?>' ?>
<Response>
   <?php        
function sip2number($sip) {   list($proto, $url, $port) = split(":", $sip);
   list($number, $domain) = split("@", $url);   return $number;
}

echo '<Dial callerId="+1' . sip2number($_REQUEST['From']) . '">' . sip2number($_REQUEST['To']) . '</Dial>';
?>
</Response>