If no link identifier is specified, the last opened link is assumed.
fbsql_database_password() sets and retrieves the database password used by the connection. if a database is protected by a database password, the user must call this function before calling fbsql_select_db(). if the second optional parameter is given the function sets the database password for the specified link identifier. If no link identifier is specified, the last opened link is assumed. If no link is open, the function will try to establish a link as if fbsql_connect() was called, and use it.