Because of the Twitter API 1.0 retirement as of June 11th 2013, the script below does not work anymore.
// Create curl resource 
$ch = curl_init(); 
// Set u         
        
The code pasted by Rivers is great. Thanks a lot! I'm new here and can't comment, I'd just want to answer to the question from javiervd (How would you set the screen_name and count with this approach?), as I've lost a lot of time to figure it out.
You need to add the parameters both to the URL and to the signature creating process. Creating a signature is the article that helped me. Here is my code:
$oauth = array(
           'screen_name' => 'DwightHoward',
           'count' => 2,
           'oauth_consumer_key' => $consumer_key,
           'oauth_nonce' => time(),
           'oauth_signature_method' => 'HMAC-SHA1',
           'oauth_token' => $oauth_access_token,
           'oauth_timestamp' => time(),
           'oauth_version' => '1.0'
         );
$options = array(
             CURLOPT_HTTPHEADER => $header,
             //CURLOPT_POSTFIELDS => $postfields,
             CURLOPT_HEADER => false,
             CURLOPT_URL => $url . '?screen_name=DwightHoward&count=2',
             CURLOPT_RETURNTRANSFER => true, CURLOPT_SSL_VERIFYPEER => false
           );