prestashop, sometimes save does not work?

Thats why i hated PHP.
It took me half a day to finally realize, prestashop was posting too much variables on the product form with my additional fields.
There wasn't any error, but the form just return back to the front page with no exception, no error logs...
just plain - "not working".

after testing

echo "keys: ".count(array_keys($_REQUEST));

i found 990 keys posted.
then i went into whm and change php.ini in /usr/local/lib

max_input_vars 5000

then i found the keys posted is 1800+ keys..

PHP sucks!