how get number of twitter followers in wordpress

You would replace this:

$dataOrig = file_get_contents('http://twitter.com/users/show/'.$twitter_user);
if (is_wp_error($dataOrig)) {
     return 'Error!!!';
}else{
     $profile = new SimpleXMLElement ( $dataOrig );
     $countOrig = $profile->followers_count;
     $count = strval ( $countOrig );
     } 

With this:

$dataOrig = wp_remote_get('http://twitter.com/users/show/'.$twitter_user);
if (is_wp_error($dataOrig)) {
     return 'Error!!!';
} else {
     $profile = new SimpleXMLElement ( $dataOrig['body'] );
     $countOrig = $profile->followers_count;
     $count = strval ( $countOrig );
} 

Note that wp_remote_get returns an array with the body of the page in body.

Edit: Using wp_remote_retrieve_body…

$dataOrig = wp_remote_get( 'https://twitter.com/users/show/'.$twitter_user );

if ( is_wp_error( $dataOrig ) ) {
  return printf( '%s: %s', $dataOrig->get_error_code(), $dataOrig->get_error_message );
} elseif( 
  empty( $dataOrig )
  OR 200 !== wp_remote_retrieve_response_code( $dataOrig )
  OR 'OK' !== wp_remote_retrieve_response_message( $dataOrig )
) {
  return _e( 'Nothing available', 'your_textdomain' );
} else {
  $dataContent = wp_remote_retrieve_body( $dataOrig );
  $profile = new SimpleXMLElement ( $dataContent );
  $countOrig = $profile->followers_count;
  $count = strval ( $countOrig );
}