无法加载外部实体“”

Basically this is a search bar and I take the searched for term and put it in the api call url, however i'm getting

Warning: simplexml_load_file() [function.simplexml-load-file]: I/O warning : failed to load external entity ""

any ideas?

code:

if (!empty($_POST['searchbird'])){
    $searchbird=rawurlencode($_POST['searchbird']);
    $searchCode = "http://ebird.org/ws1.1/data/obs/region_spp/recent?rtype=subnational2&r=US-AZ-013&sci=$searchbird";
    $url_headers = @get_headers($searchCode);

    if($url_headers[0] == 'HTTP/1.1 200 OK') {
        $xml = simplexml_load_file($url);

        print_r($xml);

    } else {
        // Error
        echo $searchCode;
        print_r($url_headers);
        exit("failed to load XML");
    }


} else {
    $searchbird = '';
    $form = "<form method='post'>
       <strong>Enter the name of a Bird</strong>
       <input type='text' name='searchbird' value='$searchbird' />
       <input type='submit' name='submit' value='submit' />
    </form>";
    echo $form;
}

You want to change the variable in the function from $url to $searchCode as the $url variable is empty and wasn't set anywhere.

if (!empty($_POST['searchbird'])){
    $searchbird=rawurlencode($_POST['searchbird']);
    $searchCode = "http://ebird.org/ws1.1/data/obs/region_spp/recent?rtype=subnational2&r=US-AZ-013&sci=$searchbird";
    $url_headers = @get_headers($searchCode);

    if($url_headers[0] == 'HTTP/1.1 200 OK') {
        $xml = simplexml_load_file($searchCode);

        print_r($xml);
 ....