mysqli

Can I check if PDO and MySQLI extension is enabled on my Plesk hosting? my forum script is requiring MySQLI and PDO but I don't know where to check if they are enabled. If not, how can I activate these features?

In my config file of my website cms, it decaled this variable $config['Database']['dbtype'] = 'mysqli'; and on old version $config['Database']['dbtype'] = 'mysql'; Which should I use? why? Can you tell me what is the difference between mysqli and mysql? which one is right for you? thanks...