Wordpress Ajax request will not refresh

(sorry for not good english)

I have a problem on my wordpress theme (custom theme). I have a box in my sidebar with my last 5 tweets. This box is called with ajax but the content will not change if I add a tweet on twitter, even on refresh page.

The way i do:

In my main.js

jQuery.ajax({
      type:'POST',
      data:{action:'twitter_action', username:'xxxx'},
      url: "http://www.ndwi.ch/wp-admin/admin-ajax.php",
      success: function(value) {
        jQuery("#lasttweets").html(value)
      }
    });

In function.php

add_action('wp_ajax_twitter_action', 'wp_echoTwitter');
add_action('wp_ajax_nopriv_twitter_action', 'wp_echoTwitter');

function wp_echoTwitter( ){

$username = $_POST['username'];
$numb = 6;

 include_once(ABSPATH.WPINC.'/rss.php');

 $tweet = fetch_rss("http://search.twitter.com/search.atom?q=from:" . $username . "&rpp=" . $numb );
 $text = '<ul class="twitter t' . time() . '">';
 for($i=0; $i<$numb; $i++){
    $text .= "<li>" .  html_开发者_Python百科entity_decode( $tweet->items[$i]['atom_content'] )  . "</li>";
 }
 $text .= "</ul>";
 die( $text );

}

Do I make something wrong ? Not a long time I work with wordpress. Thanks in advance for your help.

---

Problem solved. Richard M said:

When using the fetch_rss function (which is deprecated) Wordpress will cache the feed for one hour, which may be your problem.

The replacement for deprecated function is fetch_feed: http://codex.wordpress.org/Function_Reference/fetch_feed