$apikey = 'YOUR API KEY HERE';
$appid = 'APPLICATIONID';
$email = 'your@email.COM';
$passwd = 'PASSWORD';
$params = http_build_query(array(
   'email' => $email,'password'=> $passwd,'application_id' => $appid,'signature' => sha1("$email$passwd$appid$apikey"),'response_format' => 'json'
));
$fp = foPEn('https://www.mediafire.com/api/user/get_session_token.PHP?'.$params,'r');
$JSON = stream_get_contents($fp);
$obj = json_decode($json);
fclose($fp);

$session = $obj->response->session_token;

现在用这个新的$session键上传一个文件.

$filecontents = file_get_contents("/path/to/file");
$filesize = strlen($filecontents);
$opts = array(
  'http'=>array(
    'method'=>"POST",'header'=> "x-filename : ANYFILENAMEYOUWANT\r\n".
               "x-filesize : $filesize\r\n"
  )
);
$context = stream_context_create($opts);
$params = http_build_query(array(
    "session_token" => $session
));
$fp = fopen('http://www.mediafire.com/api/upload/upload.PHP?'.$params,'r',false,$context);
fwrITe($fp,$filecontents);
$result = stream_get_contents($fp);
fclose($fp);

重要说明：请亲自尝试.我没有测试过.刚看到API并编写了这段代码.所以它不会在第一次工作.您需要进行修改才能使其正常工作.