PHP Restrict access to file based on created time of the file

restrict_file.php

<?php

$requestedPath = '...';
$service = $app['service.filesystem'];
$fullFilePath = realpath($requestedPath);

// If the file path cannot be found then stop proceeding
if(!$fullFilePath) die('INVALID');
$fileStat = stat($fullFilePath);
$finalAllowedTimeStamp = strtotime("2017-02-01");

// If the file has been created after the max allowed time then stop proceeding
if($fileStat['mtime'] > $finalAllowedTimeStamp) die('INVALID');

// Continue reading the file

// Get the path information
$filePathInfo = pathinfo($fullFilePath);

// Get the mime type of the file
$mimeType = mime_content_type($filePathInfo['basename']);

// Set the correct headers so that browser can open the file
header("Content-type: {$mimeType}");
header('Content-Length: ' . filesize($fullFilePath));
header('Content-Disposition: filename="'.$filePathInfo['basename'].'"');
readfile($fullFilePath);
die();