VK API загрузка фото

При отправке multipart/form-data по полученному url, запрос

https://pu.vk.com/c639830/upload.php?act=do_add&mid=xxx&aid=-14&gid=0&hash=xxxx&rhash=xxxxx&swfupload=1&api=1&wallphoto=1

от сервера VK приходит полуправильный ответ(есть сервер, и hash, нету фото). Вот как приходит:

{"server":87899,"photo":"[]","hash":"xxxx"}

Вот как ожидается:

{
"server":123456,
"photos_list":"[{\"photo\":\"e9f2eba71b:y\",\"sizes\":[[\"s\",\"123456852\",\"e65f\",\"Br4ir9YAvO8\",75,41],[\"m\",\"123456852\",\"e660\",\"Lqpe1N8s8zY\",130,71],[\"x\",\"123456852\",\"e661\",\"tRFbnaIP_4c\",604,330],[\"y\",\"123456852\",\"e662\",\"8JhBOy0qR6o\",748,409],[\"o\",\"123456852\",\"e663\",\"fn5KcewNluM\",130,87],[\"p\",\"123456852\",\"e664\",\"ESWOdpl7bvY\",200,133],\"kid\":\"569c3da3b168b347315aa5adc92a953a\",\"debug\":\"xsymyxyyyoypyqyry\"}]",
"aid":98754321,
"hash":"22b333dbbef7cd9b1f9829b5f8713f86"
}

Тестовый код

function get_web_page($url, $post = null)
{
    $options = array(
        CURLOPT_RETURNTRANSFER => true,     // return web page
        CURLOPT_HEADER         => false,    // don't return headers
        CURLOPT_FOLLOWLOCATION => true,     // follow redirects
        CURLOPT_ENCODING       => "",       // handle all encodings
        CURLOPT_USERAGENT      => "spider", // who am i
        CURLOPT_AUTOREFERER    => true,     // set referer on redirect
        CURLOPT_CONNECTTIMEOUT => 120,      // timeout on connect
        CURLOPT_TIMEOUT        => 120,      // timeout on response
        CURLOPT_MAXREDIRS      => 10,       // stop after 10 redirects
        CURLOPT_SSL_VERIFYPEER => false     // Disabled SSL Cert checks
    );

    $ch      = curl_init( $url );
    curl_setopt_array( $ch, $options );
    if($post){
      curl_setopt($ch, CURLOPT_POST, 1);
      curl_setopt($ch, CURLOPT_POSTFIELDS, $post);
    }
    $content = curl_exec( $ch );
    $err     = curl_errno( $ch );
    $errmsg  = curl_error( $ch );
    $header  = curl_getinfo( $ch );
    curl_close( $ch );
    $header['errno']   = $err;
    $header['errmsg']  = $errmsg;
    $header['content'] = $content;
    return $header;
}
$for_upload = get_web_page("https://api.vk.com/method/photos.getWallUploadServer?access_token=".$token."&group_id".$id);
$url_upload = json_decode($for_upload['content'])->response->upload_url;
$upload = get_web_page($url_upload, array("file1" => "test.jpg"));

В чем может быть проблема?