This is only part of functions.php - You can view this file in context here: https://github.com/caseysoftware/upgrading-google-voice-with-Twilio

functions.php

<?php

// There is not the entire file, download the full package from Github.
function process_command($message)
{
    $message = preg_replace('!\s+!', ' ', $message);
    $words = explode(' ', $message);

    $response = "Unknown command. Use: allow, block, remove, status, or name with a phone number to manage your lists";

    if (2 > count($words)) {
        return $response;
    }

    $command = $words[0];
    $number  = preg_replace("/[^0-9]/", "", $words[1]);

    $perms = new Permissions();

    switch($command) {
        case 'allow':       // add to whitelist
            $result = $perms->updateList($number, 'white');
            $response = ($result) ? "$number has been added to your whitelist" :
                "An error has occured adding $number to your whitelist";
            break;
        case 'block':       // add to blacklist
            $result = $perms->updateList($number, 'black');
            $response = ($result) ? "$number has been added to your blacklist" :
                "An error has occured adding $number to your blacklist";
            break;
        case 'remove':      // remove from either list
            $result = $perms->removeNumber($number);
            $response = ($result) ? "$number has been removed from your lists" :
                "An error has occured removing $number from your lists";
            break;
        case 'status':      // check where the number is
            $result = find_in_list($number);
            $response = ('' == $result) ? "$number was not in your lists" :
                "$number is in your {$result}list";
            break;
        default:
            // do nothing, let the "unknown" response from above fall through
    }

    return $response;
}