if you don't have curl try using something like this.
PHP Code: 
  $context stream_context_create(array( 
    
'http' => array( 
      
'method'  => 'POST'
      
'header'  => sprintf("Authorization: Basic %s\r\n"base64_encode($username.':'.$password)). 
                   
"Content-type: application/x-www-form-urlencoded\r\n"
      
'content' => http_build_query(array('status' => $message)), 
      
'timeout' => 5
    ), 
  )); 
  
$ret file_get_contents('http://twitter.com/statuses/update.xml'false$context); 
  
  return 
false !== $ret
You will need to modify it for your input to the site.