JavaScript答案

(function() {
    main();
    function main() { 
        jQuery(document).ready(function($) { 
            $.ajax({
                type: 'post',
                url: 'http://example.com/search.php',
                data: { value: '123' },
                cache: false,
                success: function(returndata) {
                    $('#widget').html(returndata);
                }
            });
        });
    }
})(); 

<script src="http://example.com/widget.js" type="text/javascript"></script>
<div id="widget"></div>

When I paste widget on my site, it works perfectly and I get answers who is in div "widget" but if I paste this:

<script src="http://example.com/widget.js" type="text/javascript"></script>
<div id="widget"></div>

for another page it's not working. Can anyone help?

As of your comment, you are experiencing Cross domain restrictions (Same-origin policy). A workable solution for this is to serve your content from "search.php" as jsonp instead.

<?php

header('content-type: application/json; charset=utf-8');
$searchResults= array("Article 1", "Article 2", "Article 3");
echo $_GET['callback'] . '('.json_encode($searchResults).')';

?>

In your jQuery $.ajax, you should set the dataType to "jsonp, and perhaps set the parameter crossDomain to true aswell.

(function() {
    main();
    function main() { 
        jQuery(document).ready(function($) { 
            $.ajax({
                type: 'post',
                dataType: 'jsonp',
                crossDomain: true, // Shouldent be neccesary.
                url: 'http://example.com/search.php',
                data: { value: '123' },
                cache: false,
                success: function(returndata) {
                    $('#widget').html(returndata);
                }
            });
        });
    }
})(); 

Hope it works out for you.