Increase max execution time in PHP

Question

My server support post_max_size 192MB and max_execution_time 600 sec so when I upload a 100MB file after 600 sec the execution stops. Is there a way to increase the execution size?

I tried this:

ini_set ( 'max_execution_time', 1200); 
if(move_uploaded_file($_FILES['Video']['tmp_name'],$tmppath)) {
  // ...
} 

But it didn't work.