Selenium returns null ({"ELEMENT":"0"}) on my every element finding attempts.

[abtvah]

PHP-Webdiver also returns null, however to test things out I've written my own script, here is a brief description of the problem:

I have an Ubuntu server running on a VPS with LXDE and Firefox been installed. Also I've started Selenium server using this command:

java -jar selenium-server-standalone-2.33.0.jar

it is now running and listens on localhost port 4444. To connect to selenium server via PHP I use this simple script :

$url = "http://www.amazon.com";
$dc = array("browserName" => "firefox",
                 "version" => "",
                 "platform" => "ANY",
                 "javascriptEnabled" => True);

// To get the session id
$session_id = get_id($dc);  

// Open 'amazon.com'
$new_map = "/session/".$session_id."/url";
$result = curl_transfer('POST', array('url' => $url), $new_map);

// Wait until the page completely been loaded
$new_map = "/session".$session_id."/timeouts/implicit_wait";
curl_transfer('POST', array('ms' => 7000), $new_map);

// Find an element, here is the Brazil link at the bottom of the page
$new_map = "/session/".$session_id."/element";
$t = curl_transfer('POST', array('using' => 'link text', 'value' => 'Brazil'), $new_map);

print_r($t);


function curl_transfer ($method, $params, $map){
   $path = 'http://localhost:4444/wd/hub'.$map;
   $c = curl_init($path);
   if ($method === 'POST') {

       $encoded_params = json_encode($params);

       curl_setopt($c, CURLOPT_CONNECTTIMEOUT, 30);
       curl_setopt($c, CURLINFO_HEADER_OUT, true);
       curl_setopt($c, CURLOPT_RETURNTRANSFER, true);
       curl_setopt($c, CURLOPT_HEADER, true);
       curl_setopt($c, CURLOPT_HTTPHEADER, array(
               'Content-Type: application/json;charset=UTF-8',
               'Accept: application/json',
               'Expect:'));
       curl_setopt($c, CURLOPT_POST, 1);
       curl_setopt($c, CURLOPT_POSTFIELDS, $encoded_params);

       $raw_result = curl_exec($c);
       // print_r(curl_getinfo($c)); 
       return (string)$raw_result;
   }
   if ($method === 'GET') {

      curl_setopt($c, CURLOPT_CONNECTTIMEOUT, 30);
      curl_setopt($c, CURLINFO_HEADER_OUT, true);
      curl_setopt($c, CURLOPT_RETURNTRANSFER, true);
      curl_setopt($c, CURLOPT_HEADER, true);

  $raw_result = curl_exec($c);
      // print_r(curl_getinfo($c)); 
      return (string)$raw_result;
   }
}

function get_id ($dc){
   $result = curl_transfer('POST', array('desiredCapabilities' => $dc), '/session');
   $array_result = explode ("\r\n", $result);
   $id = str_replace("Location: http://localhost:4444/wd/hub/session/", "", $array_result[6]);
   return $id;
}

Everything works fine, the session is being started and Firefox is navigated to Amazon.com,
however with every attempts that I did to find an element I get this as the return object:

{"status":0,"sessionId":"3a0d5939-595e-40d6-88c8-fe6f22a165dd","value":{"ELEMENT":"0"},"state":null,"class":"org.openqa.selenium.remote.Response","hCode":15920450}

It seems that the element hasn't been found at all. What's wrong here? Any idea?