last blog:　Writing A Twitter Client Using PHP (1): Consumer Requests Request Token 

Here is the step B Service Provider Grants Request Token.
At the last blog, I got url, something as below:
https://twitter.com/oauth/request_token?oauth_callback=http%3A%2F%2Flocalhost%2Fitwitter%2F&oauth_consumer_key=fwwaw3m5sQq4L3M6aXV1jg
&oauth_nonce=817d10a677547378dbef3547c5545fdb&oauth_signature=Hv48dvKEbWAn4tG4JSEs0UbM1so%3D&oauth_signature_method=HMAC-SHA1&oauth_timestamp=1295839203&oauth_version=1.0a

Here curl is used. The function is as below:
 
function http( $url) {  
  $ch = curl_init($url);  
  curl_setopt($ch, CURLOPT_HEADER, false); 
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); 
  curl_setopt($ch, CURLOPT_FRESH_CONNECT,true); 
  curl_setopt($ch, CURLOPT_USERAGENT, “Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)”);
  curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true); 
  curl_setopt($ch, CURLOPT_MAXREDIRS, 5);         
  curl_setopt($ch, CURLOPT_COOKIEJAR, ‘cookie.txt’); 
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false); 
  curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);      
  $content = curl_exec($ch);  
  curl_close($ch); 
  return $content;
}

Then use echo http($url);

Then I gets the string like below from the Twitter server：

oauth_token=sNwJ4Km398PwLdOOjxBcER7KQ2U8P9uPocLblUaAY
&oauth_token_secret=SMVXvhsBWX9qbwbZNsukn5qc2Ex3vLUV405sQyrrU&oauth_callback_confirmed=true

Then turn this string to an Array and put in a variable:

$oauth_responses = http($url);
$oauth_responses = split(‘&’, $oauth_responses);
$parsed_parameters = array();
foreach ($oauth_responses as $oauth_response) {
  $split = split(‘=’, $oauth_response, 2);
  $parameter = $split[0];
  $value = $split[1];
  if (isset($parsed_parameters[$parameter])) {
 if (is_scalar($parsed_parameters[$parameter])) {
   $parsed_parameters[$parameter] = array($parsed_parameters[$parameter]);
 }
 $parsed_parameters[$parameter][] = $value;
  } else {
   $parsed_parameters[$parameter] = $value;
 }
  }

The value of $parsed_parameters is something like below：

Array ( [oauth_token] => sNwJ4Km398PwLdOOjxBcER7KQ2U8P9uPocLblUaAY [oauth_token_secret] => SMVXvhsBWX9qbwbZNsukn5qc2Ex3vLUV405sQyrrU [oauth_callback_confirmed] => true )

Then get the value of oauth_token, and add it behind the request. The code is as below: 
 
$oauth_token = $parsed_parameters[‘oauth_token’];
$url2 = “http://api.twitter.com/oauth/authorize?oauth_token=” . $oauth_token;

This is the step C in the diagram above.