listing all active sip channels

<?php

$channel=shell_exec("asterisk -x \" core show channels\" | awk '{print $1}' | awk '/SIP/{print}'");

$channelist=explode("\n",$channel);
foreach($channelist as $key=> $value) {
if (preg_match("/\bSIP\b/i", $value,$match)){

echo "$key : $value\n";
}
}
?>