Correct property name. It's just 'tableprefix', without the 'db' prefix.
Correct property name. It's 'dbpassword', with the 'db' prefix.
There is no property such as dbusername. It's 'dbuser'.
No function as oci_last_error. It's oci_error.
Add getLastError()
Use getLastError() everywhere.
fixing PHPDoc and spelling