<form>
<div style="text-align:center;background: #f3f3f3;padding: 40px 40px 50px;margin:-10px;border-bottom:5px solid #ccc;">
    <span class="spam1"><a href="http://westhost.com.br/teste/index2.php"> REINICIAR</a></span>
    <td> <input style="height:50px;" type="text" name="clientid" />
         <input class="submit" type="submit" name="Pesquisar" value="Pesquisar ID"></td>
</div>
 </form>


  <?php
if(isset($_GET['Pesquisar'])){ /* A ação só será executada após clicar no botão Submit */


 $url = "https://westhost.com.br/painel/includes/api.php"; # URL to WHMCS API file goes here
 $username = "root"; # Admin username goes here
 $password = "asdsadsadsa"; # Admin password goes here

 $postfields = array();
 $postfields["username"] = $username;
$postfields["password"] = md5($password);
 $postfields["action"] = "getclients";
//$postfields["clientid"] = "297";
 $postfields["stats"] = true;
  $postfields["responsetype"] = "xml";