Actually, upon further reading on the file_get_contents() function:

// Create a stream
$opts = [
    "http" => [
        "method" => "GET",
        "header" => "Accept-language: en\r\n" .
            "Cookie: foo=bar\r\n"
    ]
];

$context = stream_context_create($opts);

// Open the file using the HTTP headers set above
$file = file_get_contents('http://www.example.com/', false, $context);

You may be able to follow this pattern to achieve what you are seeking to, I haven't personally tested this though. (and if it doesn't work, feel free to check out my other answer)