This is a simple script using the Twilio PHP Helper library to retrieve Recordings within a certain date range and then delete them.

delete-recordings.php

<?php
// Get the PHP helper library from https://twilio.com/docs/libraries/php
require_once '/path/to/vendor/autoload.php';
use Twilio\Rest\Client;

// Your Account Sid and Auth Token from twilio.com/console
$sid    = "ACaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
$token  = "your_auth_token";

$twilio = new Client($sid, $token);

$recordings = $twilio->recordings
                     ->read(array(
                                'callSid' => "CAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
                                'dateCreatedBefore' => '2011-08-01'
                                'dateCreatedAfter' => '2011-07-05 08:00:00'
                            ), 50);

foreach ($recordings as $record) {
    echo "Deleting: " . $recording->sid . " -- " . $recording->date_created . "\n";
    $client->recordings($recording->sid)->delete();
}