Fix php error Message: Module 'pdo_mysql' already loaded

Hi everyone, Since the upgrade of PHP to 7.2 the codeigniter webapp keeps showing this error message: A PHP Error was encountered Severity: Core Warning Message: Module 'pdo_mysql' already loaded Filename: Unknown Although PHP error reporting is turned OFF in php.ini and edited /etc/security/limits.conf to set hard core 0. Tried to change back PHP version - didn't help. Tried to identify multiple PDO modules being loaded in php.ini - negative. Nothing helped.