YML, YQL, PHP, CSS, and HTML for YAP app search box referenced in YDN blog post: http://developer.yahoo.net/blog/archives/2009/11/yahoo_app_searchbox.html

gistfile1.php

<?php
$search_term = $_GET['search_term'];

if($search_term){

   //http://developer.yahoo.com/yql/console/?q=select%20*%20from%20search.web%20where%20query%3D%22pizza%22
   $yql_search_url = "http://query.yahooapis.com/v1/public/yql?"
		."q=select%20*%20from%20search.web%20where%20query%3D%22$search_term%22&"
		."format=json&diagnostics=false&callback=";

   $ch = curl_init($yql_search_url);
   curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
   $response = json_decode(curl_exec($ch));
   curl_close($ch);
}
?>

<? if($response->query->results->result): ?>
   <ul id="results">
       <? foreach($response->query->results->result as $result): ?>
           <li>
               <a href="<?= $result->clickUrl ?>"><?= $result->title ?></a><br/>
               <?= $result->abstract ?>
           </li>
       <? endforeach ?>
   </ul>
<? else: ?>
   <style>
   #wrapper ul {
       padding-left: 0px;
   }
   #wrapper ul li {
       margin-bottom: 1ex;
   }
   </style>
   <div id="wrapper">
       <yml:form replace="results">
           <input name="search_term"/>
           <input type="submit" value="Search"/>
       </yml:form>
       <ul id="results"></ul>
   </div>
<? endif ?>