PDO_sqlITE is a driver that
implements the PHP Data Objects (PDO)
interface to enable access to sqlite 3
databases.

In PHP 5.1,the sqlite extension also
provides a driver for sqlite 2
databases; while it is not technically
a part of the PDO_sqlITE driver,it
behaves similarly,so it is documented
alongside it. The sqlite 2 driver for
PDO is provided primarily to make it
easier to import legacy sqlite 2
database files into an application
that uses the faster,more efficient
sqlite 3 driver. As a result,the
sqlite 2 driver is not as feature-rich
as the sqlite 3 driver.

从http://php.net/manual/en/ref.pdo-sqlite.php起