Hello,
I have installed HestiaCP without MySQL/MariaDB database server on it. Instead, I have a separate MariaDB database server (dockerized) on the same server.
The application (website) that I’m trying to configure in HestiaCP fails to detect de corresponding extension for pdo_mysql.
I already enabled it by uncommeting the line ‘;extension=pdo_mysql’, but what do to next from HestiaCP?
Ok, fixed it by installing it manually:
apt-get install php7.4-mysql
And no need to edit the php.ini file at all. So, I reverted it back:
Before: extension=pdo_mysql
After: ;extension=pdo_mysql
But, shouldn’t it be installed automatically by HestiaCP when we select a php package from the list to install? Or HestiaCP doesn’t install the mysql version if the use doesn’t have any local database server running within Hestia?
Yes to both questions 
The script used to add PHP versions (v-add-web-php) , has in the list these packages:
mph="php$version-common php$version-mbstring php$version-bcmath php$version-cli php$version-curl
php$version-fpm php$version-gd php$version-intl php$version-mysql
php$version-soap php$version-xml php$version-zip php$version-json php$version-bz2
php$version-pspell php$version-imagick php$version-pgsql php$version-imap php$version-ldap"
And it includes mysql module for php but later, it checks whether you have mysql/mariadb installed and if you didn’t install it, Hestia removes the package from the list:
if ! echo "$DB_SYSTEM" | grep -w 'mysql' > /dev/null; then
mph=$(echo "$mph" | sed -e "s/php$version-mysql//")
fi
Ohh, I understand now.
Thank you very much for the explanation!