Upload 6 pdf in single PHP form

if i want to upload 开发者_如何学C6 pdf on server using php.

each pdf is approx 8-10 mb.

My PHP form to upload pdf is like this

I have also increase my server max-upload-size and max-post-size upto 200 MB and also increase max execution time.

But i am getting internal server 500 error.

Whats wrong with this?

Any one have idea?

Thanks in advance