cURL on proxied localhost returns Access Denied - php

Question

I'm trying to access a .php file from another .php using cURL.
Both are on localhost and I'm using a proxy.
THE PROBLEM
If I try to access using postman or direct on the browser, the desired file returns correctly.
However, everytime that I try to access this file from another .php file using cURL, and passing all the proxy and auth values, it gives me the following:
Access Denied (authentication_failed)
Your credentials could not be authenticated: "Credentials are missing.". You will not be permitted access until your credentials can be verified.
This is typically caused by an incorrect username and/or password, but could also be caused by network problems.
For assistance, contact your network support team.
Her is my cURL:
$curl = curl_init();
curl_setopt_array($curl,array(
CURLOPT_PROXY => "proxy.myspecificproxy.com.br",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_URL => "localhost/MyDesiredFile.php?param=test&mail=test%40test.com",
CURLOPT_FOLLOWLOCATION => true,
CURLOPT_PROXYUSERPWD => "myuser:mypassword123",
CURLOPT_PROXYPORT => "8080",
CURLOPT_PROXYTYPE => 'HTTP',
));
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}
Any ideas?
EDIT:
Beyond trying to access via postman or browser, if I cURL directly from the command line, it works too.
EDIT
Tried to disable the proxy for local addresses, but no change in the result.

Answer 1

Is there a redirect involved? Remember that cURL doesn't follow redirects unless you tell it to, by passing the --location flag.
Does it work if you run it from the command line? Try that, and try passing --verbose and --include to see the returned headers.

Answer 2

Update your code as below
$curl = curl_init();
curl_setopt_array($curl,array(
CURLOPT_PROXY => "proxy.myspecificproxy.com.br",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_URL => "localhost/MyDesiredFile.php?param=test&mail=test%40test.com",
CURLOPT_FOLLOWLOCATION => true,
CURLOPT_PROXYUSERPWD => "myuser:mypassword123",
CURLOPT_PROXYPORT => "8080",
CURLOPT_PROXYTYPE => 'HTTP',
));
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}

Answer 3

<?php
$curl = curl_init();
curl_setopt_array($curl,array(
CURLOPT_RETURNTRANSFER => true,
CURLOPT_URL => "http://localhost/",
CURLOPT_FOLLOWLOCATION => true,
));
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}

Answer 4

Looks like it was a misconfiguration in the privileges.
I contacted the support team of the company and the problem was solved.