为什么我的文件在php中没有正确上传？

Question

我正在使用此功能将图片上传到我的服务器。

function uploadProductImage($inputName, $uploadDir) {
    $image         = $_FILES[$inputName];
    $imagePath     = '';
    $thumbnailPath = '';

// if a file is given
    if (trim($image['tmp_name']) != '') {
        $ext       = substr(strrchr($image['name'], "."), 1);
//$extensions[$image['type']];
        // generate a random new file name to avoid name conflict
        $imagePath = md5(rand() * time()) . ".$ext";

        list($width, $height, $type, $attr) = getimagesize($image['tmp_name']);

        // make sure the image width does not exceed the
        // maximum allowed width
        if (LIMIT_PRODUCT_WIDTH && $width > MAX_PRODUCT_IMAGE_WIDTH) {
            $result    = createThumbnail($image['tmp_name'], $uploadDir .
                    $imagePath, MAX_PRODUCT_IMAGE_WIDTH);
            $imagePath = $result;
        } else {
            $result = move_uploaded_file($image['tmp_name'], $uploadDir .
                    $imagePath);
        }

        if ($result) {
            // create thumbnail
            $thumbnailPath = md5(rand() * time()) . ".$ext";
            $result        = createThumbnail($uploadDir . $imagePath, $uploadDir .
                    $thumbnailPath, THUMBNAIL_WIDTH);

            // create thumbnail failed, delete the image
            if (!$result) {
                unlink($uploadDir . $imagePath);
                $imagePath     = $thumbnailPath = '';
            } else {
                $thumbnailPath = $result;
            }
        } else {
            // the product cannot be upload / resized
            $imagePath     = $thumbnailPath = '';
        }
    }
}
}


return array('image' => $imagePath, 'thumbnail' => $thumbnailPath);
}

这就是调用时的样子： SRV_ROOT是存储文档根目录的变量。

  $images = uploadProductImage('fleImage', SRV_ROOT . 'images/product/');

在开发环境中一切正常，但当我切换到在线服务器时，它无法正常工作。