Hi Erik, thank you for your reply, I solved the issue !
From the comparison between phpinfo() and “php -i” output I found some differences, the most relevant are the following two:
- Additional .ini files are parsed from
/etc/opt/remi/php73/php.d/dir through apache, and from/etc/php.d/with CLI command; - libraries (*.so) are loaded from
/opt/remi/php73/root/usr/lib64/php/modules/dir in apache, and from/usr/lib64/php/modules/dir in CLI, even if the common files have the same date and size, of when I updated everything with yum, so both paths seem to be mainteined by yum.
After some trials, the solution was to copy pdo_mysql.so and 30-pdo_mysql.ini in their respective CLI directories. Now the question is: why have they disappeared, since occ has been working for long time before ? But I can be happy as well now. 
Thanks and bye,
S.