Using the CC_FS_BUCKET
mentioned in documentation
Using FTP (boring and slow, but it works).
Once you adquire the FS Bucket, it will provide you a HOST and other credentials.
The idea is to set the environment variable in the one app the we need to use the bucket.
something like this:
CC_FS_BUCKET=/my-bucket-folder:bucket-xxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx-fsbucket.services.clever-cloud.com
That will mount a folder to access directly to our app (** In the execution environmet **)

once this is done and deployed, we can try like this SIMPLE example:
<?php
// this script is located one folder under root, check if your case is similar and modificate the realpath(...) parameter
define("ROOT_DIR_APP", realpath(__DIR__ ."/../"));
try {
$file = $_GET['file'];
if (empty($file) || !isset($file)) {
echo "No file specified or included";
exit;
}
// check if file exists in current folder
if (file_exists(ROOT_DIR_APP . "/my-bucket-folder" . $file))
usingLocalFile(ROOT_DIR_APP . "/my-bucket-folder" . $file); // dont forget to define the ROOT_DIR_APP constant.
} catch (Exception $e) {
echo $e->getMessage();
}
function usingLocalFile($file = '')
{
$ext = pathinfo($file, PATHINFO_EXTENSION);
if (in_array($ext, ['png', 'jpg', 'jpeg', 'gif', 'bmp', 'svg']))
header('Content-Type: image/' . $ext);
else if (in_array($ext, ['pdf', 'json']))
header('Content-Type: application/' . $ext);
else
header('Content-Type: application/octet-stream');
header('Content-Disposition: inline; filename="' . basename($file) . '"');
header('Content-Length: ' . filesize($file));
header('Accept-Ranges: bytes');
@readfile($file);
echo "File Downloaded";
}
note: This will not work locally unless you create a (git-ignored) folder to simulate the bucket.
Follow this good part only in the doc
Don’t forget to replace the path of the mounted folder and the fs-bucket host with the targeted folder path (make sure the folder not exists) and your fs-bucket host