Drupal7 Database connection

Drupal7 has used PDO for database connection .PDO is noting but PHP data objects.
PDO is a PHP extension to formalise PHP's database connections by creating a uniform interface. This allows developers to create code which is portable across many databases and platforms. PDO is _not_ just another abstraction layer like PearDB although PearDB may use PDO as a backend. Those of you familiar with Perls DBI may find the syntax disturbingly familiar.