Codeigniter，当大小文件较大时，$ _FILE为空

When I upload a Image (for example, Size 10MB), return a error "No File Selected". I make log points, but the array $_FILE is empty, If I try with a image with Size 5MB It's works and return a message error about the Size of image.

I do this with Ajax, and in the POST the file exist.

The problem only happens in the server (In localhost works fine)

Is problem of PHP memory?

Try change upload_max_filesize in php.ini.