How to increase post_max_size

Hello guys,

I’m having a well-known issue, and I’ve been looking for answers, but none of them worked for me. I can’t manage to increase the post_max_size. I tried changing the post_max_size to 128M in my php.ini file, but everytime I restart apache from plesk, it sets itself again at 8M.
I don’t know what to do… I also tried to add those lines in the htaccess, didn’t work. Tried to add another php.ini file in the /wp-admin directory, didn’t work either. I tried to add some lines in the functions.php and wp-config.php, no luck either.

Could someone help me?
We have our own server, I tried to change it via ssh but I couldn’t do it, I really don’t know what to do.
Thanks guys.