<?php

    function left($str, $length) {
        return substr($str, 0, $length);
    }

    function right($str, $length) {
        return substr($str, -$length);
    }

    //enable logging
    $logging = true;



    if ($logging) {

        $req_dump = print_r($_REQUEST, TRUE);

        $fp = fopen('dynamic_set_cid.log', 'a');
        fwrite($fp, $req_dump);

    }

    // set destination number to variable
    $to = $_REQUEST['To'];

    //find area code, set to $areacode
    if (strlen($to) > 11) {

        $areacode = right(left($to,5),3);

        } else {

            $areacode = right(left($to,4),3);
        }

    if ($logging) {
        fwrite($fp, '$to = ' . $to."\r\n");
        fwrite($fp, '$areacode = ' . $areacode."\r\n");
    }

    //select outbound callerid based on area code, replace  put caller id here with actual DID you own
    switch ($areacode) {

    case "231":
        $callerid = "+1231 put caller id here";
        break;

    case "248":
        $callerid = "+1248 put caller id here";
        break;

    case "313":
        $callerid = "+1313 put caller id here";
        break;

    case "586":
        $callerid = "+1586 put caller id here";
        break;

    case "734":
        $callerid = "+1734 put caller id here";
        break;

    case "810":
        $callerid = "+1810 put caller id here";
        break;
    }

    //remove * from destination number
    $dest_number = str_replace("*", "", $to);

    if ($logging) {
        fwrite($fp, '$dest_number = ' . $dest_number."\r\n");
        fwrite($fp, '$callerid = ' . $callerid."\r\n");
        fclose($fp);
    }

    //create response
    header("content-type: text/xml");
    echo "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n";
?>

<Response>
    <Dial callerId="<?php echo $callerid ?>">
        <Number><?php echo $dest_number ?></Number>
    </Dial>
</Response>