ResultSetMetaData in PHP - Mailing list pgsql-php

I am just use PHP.  I have two questions:

1. When I use OID, how can I get a current OID and lock it and use it
before I insert a record, as nextval(..) does, in PHP?
2. How can I use PHP to get the structure of a table, like
ResultSetMetaData in JAVA?

Thanks.

Zhidian Du