public function onUploadFileStart($in)
{
$this->freezeInput();
FileSystem::tempnam(ini_get('upload_tmp_dir'), 'php', function ($fp) use($in) {
if (!$fp) {
$in->curPart['fp'] = false;
$in->curPart['error'] = UPLOAD_ERR_NO_TMP_DIR;
} else {
$in->curPart['fp'] = $fp;
$in->curPart['tmp_name'] = $fp->path;
}
$this->unfreezeInput();
});
}