PHP Curl Downloader with resume support

downloader.php

<?php
set_time_limit(0);
ignore_user_abort(true);
$url	= "http://web.shit/backup.zip";

$ch = curl_init($url);
$to_file	= 'web.zip';
$opt	= array();
if(is_file($to_file))
{
	$sz	= filesize($to_file);
	$opt[CURLOPT_RANGE] = $sz . "-";
	
}
$opt[CURLOPT_SSL_VERIFYPEER]= false;
$opt[CURLOPT_FILE]	= fopen($to_file, 'a');
$opt[CURLOPT_USERAGENT] = 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.2357.124 Safari/537.36';
curl_setopt_array($ch, $opt);
curl_exec($ch);
$grab_info	= curl_getinfo($ch);
fclose($opt[CURLOPT_FILE]);

print_r($grab_info);