LinkedIn API OAuth Problem - php

Question

I'm using the PEAR OAuth Class to access the LinkedIn developer API and I've come across a bit of a problem. I can authorize my application but when it comes to getting an accessToken I'm receiving this error:
Edit:
Code after Adam's suggestions
public function oauth_access()
{
session_start();
$token = $_GET['oauth_token'];
$verifier = $_GET['oauth_verifier'];
$secret = $_SESSION['trequest_token_secret'];
$key = "****";
$secret = "****";
$oauthc = new OAuth($key, $secret, OAUTH_SIG_METHOD_HMACSHA1, OAUTH_AUTH_TYPE_AUTHORIZATION);
$oauthc->setToken($token, $secret);
$oauthc->setNonce(rand());
try
{
$access_token_info = $oauthc->getAccessToken("https://api.linkedin.com/uas/oauth/accessToken");
$_SESSION['laccess_oauth_token']= $access_token_info['oauth_token'];
$_SESSION['laccess_oauth_token_secret']= $access_token_info['oauth_token_secret'];
$_SESSION['loauth_verifier'] = $verifier;
}
catch (OAuthException $e)
{
echo $e->getMessage();
}
}
But I'm now getting a different error:
Invalid auth/bad request (got a 401, expected HTTP/1.1 20X or a redirect)

Answer 1

You don't need to manually compute the signature, as pecl/oauth will do that for you.
Also, you're telling the library to pass the data in the Authorization HTTP header. That is a good place to have it. Then you are passing it via a query parameter. That is permitted, but less optimal. (You may actually be passing it in two places.) Also, pecl/oauth will automatically generate the proper timestamp.
When I first started, I found this blog post to be a good first start.
Or you can use the LinkedIn PHP library listed by Paul. It's also a good place to begin, if you don't want to reuse pecl/oauth because you're using that someplace else.