gistfile1.php

<?php

require 'OAuth.php';

$consumer = new OAuthConsumer('consumer-key', 'consumer-secret');

$token    = new OAuthToken('token-key', 'token-secret'); // can be both request and access-token
// of course it needs to be an access-token to perform authorized request, but for the call to
// exchange your request-token for an access-token, this needs to be the request-token

$params = array(
  'here' => 'is list of your non oauth_*-parameters',
  'in' => 'a nice an convenient list'
);

$signature_method = new OAuthSignatureMethod_HMAC_SHA1(); // Or whatever SignatureMethod you want to use

$req = OAuthRequest::from_consumer_and_token(
  $consumer,
  $token,
  'GET', // Or POST if you need to do POST requests
  'http://service-provider.example.com/end_point', // Your URL
  $params
);
$req->sign_request($signature_method, $consumer, $token);
// By now the request is signed and contained in the OAuthRequest..

// So now we just need to send it along - this is an example using cURL
$curl = curl_init();

$_params = $req->get_parameters();
foreach( array_keys($_params) AS $i )
  if( substr($i, 0, 6) == 'oauth_' ) 
    unset($_params[$i]);
// Now $_params contains a list of your parameters without the oauth_*-parameters which we 
// wil send in the header
				
$url = $req->get_normalized_http_url();
if( $req->get_normalized_http_method() == 'POST' ) {
  curl_setopt($curl, CURLOPT_POST, true);
  curl_setopt($curl, CURLOPT_POSTFIELDS, http_build_query($_params) );
} else {
  if( count($params) )
    $url .= '?' . http_build_query($_params);
}
// And we added the non oauth_* parameters to the request
				
curl_setopt($curl, CURLOPT_URL, $url);
// Set the URL

curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);		
// We like returntransfer ;)

curl_setopt($curl, CURLOPT_HTTPHEADER, array(
  $req->to_header()
));
// Set the Authorization-header containing the oauth_* parameters		

$respone = curl_exec($curl);
// There, request performed - response in $response