Description:
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When using CURLOPT_USERPWD within a cURL request u have to provide both username AND password to work properly.

I had a problem with accessing pages with Basicauth and NO username, just a Password.

curl then calculates the base64 wrong.

As workaround i have to calculate the base64 manually and provide it to curl via the headers option

Test script:
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$curl = curl_init('http://localhost');
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_USERPWD, ':password'); // no username
curl_setopt($curl, CURLOPT_VERBOSE, true);
$response = curl_exec($curl);
curl_close($curl);

Expected result:
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something like this in the request headers:

"Authorization: Basic OnRlc3Q="

Actual result:
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"Authorization: Basic Og=="

(only the ":")