What is the different between mysql_connect & mysqli_connect in PHP DB connection?

Answer 1

both have saem usage. but mysql_ is the old interface, its removed since php7 i believe.

Answer 2

I am also confused in
MySQL , MySQLI , PDO, and there are two veriety of MySQLI and PDO

Answer 3

mysqli_connect it is a improved function of mysql_connect and it is a recommanded to use