AMI – How to monitor registration status of SIP peers?

I am trying to find out the status of an extension through the AMI interface of VitalPBX, with PHP. How do I extract the value returned by the ExtensionState action in PHP?

<?
$oSocket = fsockopen (“XXX.XXX.XXX.XXX”, 5038, $errno, $errstr, 10);
fputs($oSocket, “Action: login\r\n”);
fputs($oSocket, “Username: user\r\n”);
fputs($oSocket, “Secret: password\r\n\r\n”);
sleep (1);
fputs($oSocket, “Action: ExtensionState\r\n”);
fputs($oSocket, “Context: extensions\r\n”);

sleep (1);

fputs($oSocket, “Action: Logoff\r\n”);
fclose($oSocket);
?>