TL;DR; If you're still having trouble after restarting apache or nginx, also try restarting the php-fpm service.
The answers here don't always satisfy the requirement to force a reload of the php.ini file. On numerous occasions I've taken these steps to be rewarded with no update, only to find the solution I need after also restarting the php-fpm service. So if restarting apache or nginx doesn't trigger a php.ini update although you know the files are updated, try restarting php-fpm as well.
To restart the service:
Note: prepend sudo if not root
Using SysV Init scripts directly:
/etc/init.d/php-fpm restart # typical
/etc/init.d/php5-fpm restart # debian-style
/etc/init.d/php7.0-fpm restart # debian-style PHP 7
Using service wrapper script
service php-fpm restart # typical
service php5-fpm restart # debian-style
service php7.0-fpm restart. # debian-style PHP 7
Using Upstart (e.g. ubuntu):
restart php7.0-fpm # typical (ubuntu is debian-based) PHP 7
restart php5-fpm # typical (ubuntu is debian-based)
restart php-fpm # uncommon
Using systemd (newer servers):
systemctl restart php-fpm.service # typical
systemctl restart php5-fpm.service # uncommon
systemctl restart php7.0-fpm.service # uncommon PHP 7
Or whatever the equivalent is on your system.
The above commands taken directly from this server fault answer