PHP + cURL gets file that shouldn't exist - php

Question

This is my first question on here and I wouldn't ask if I haven't tried nearly everything in my might already. My problem is as follows:
I got tasked to maintain an old webapp in our company and part of it was to change an old date in a html file to the current year. I did that and when I access the file with the required parameters directly it works. Now the app itself doesn't access this file directly but loads it in through something they called "proxy.php" - it defines allowed hosts and some other stuff but the thing it mostly does is get data via cURL. If I access the file that I changed through the "proxy.php" it returns a file that shouldn't exist anywhere on the server (with old content in it).
I replicated proxy.php's function down below with the same result (an old file is served):
<?php
//phpinfo();
//Proxy.php test because weird things are happening...
$url = $_GET["url"]; //The url that it gets is escaped already.
$ch = curl_init();
curl_setopt($ch, CURLOPT_HTTPGET,1);
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,TRUE);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 5);
curl_setopt($ch, CURLOPT_TIMEOUT, 15);
$xml = curl_exec ($ch);
echo $xml;
?>
I also got told by a colleague that they always only altered they date in the html file and it worked until now. I hope I provided enough information about my problem. Thank you in advance.

Answer 1

Just wanted to give a quick update as I have resolved the issue thankfully.
Deep in the configuration was an old proxy server that seemed to be serving cached files.
I changed the "proxy.php" to use a new proxy server:
$proxy = "your.proxy.server:port";
curl_setopt($ch, CURLOPT_PROXY, $proxy);
Thanks everyone for your advice :)