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 no link is open, the function will try to establish a link as if
fbsql_connect() was called, and use it.
This function does not change the database password in the database
nor can it be used to retrieve the database password for a database.
If optional and not specified,
the function will try to find an open link to the FrontBase server and if no
such link is found it will try to create one as if
fbsql_connect() was called with no arguments
database_password
The database password, as a string. If given, the function sets the
database password for the specified link identifier.
Return Values
Returns the database password associated with the link identifier.