HTTP request failed! with file get contents - php

Question

I used OAuth for Dropbox to get access token: https://blogs.dropbox.com/developers/2012/07/using-oauth-1-0-with-the-plaintext-signature-method/
But I got error message:
Warning: file_get_contents(https://api.dropbox.com/1/oauth/request_token): failed to open stream: HTTP request failed! HTTP/1.1 400 Bad Request
My PHP Code:
$Header = json_encode(array('Authorization: OAuth oauth_version="1.0"', "oauth_signature_method" => "PLAINTEXT", "oauth_consumer_key" => "XX", "oauth_signature" => "XX"));
$Options = array('http' =>
array(
'method' => 'POST',
'header' => $Header,
)
);
$Context = stream_context_create($Options);
$Result = file_get_contents("https://api.dropbox.com/1/oauth/request_token", false, $Context);
print_r($Result);

Answer 1

Based on the documentation at http://php.net/manual/en/context.http.php, it looks like the header option is just a normal string, not json_encoded. Alternatively, you should be able to use a numerically indexed array of headers, like so:
$Header = array(
"Authorization: OAuth oauth_version=\"1.0\", oauth_signature_method=\"PLAINTEXT\", oauth_consumer_key=\"XXXXX\", oauth_signature=\"XXXXX&\"\r\n"
);
$Options = array('http' =>
array(
'method' => 'POST',
'header' => $Header,
)
);

Answer 2

This is wrong:
$Header = json_encode(array('Authorization: OAuth oauth_version="1.0"', "oauth_signature_method" => "PLAINTEXT", "oauth_consumer_key" => "XX", "oauth_signature" => "XX"));
The header paramter in an http stream is either a simple single string containing one single header key: value, or an array of key: value strings. You're stuffing in a single json string as your header, meaning it's NOT a valid http header.
Remove the json_encode() part completely. $Header = array(...) is all you need.