The PHP odbc driver doesn't manage errors correctly. Here is the complete explanation the Easysoft team gave me:

From: Martin J. Evans <martin@easysoft.com>
"Tomas V.V.Cox" wrote:
> 
> Hi,
> 
> I'm getting a little bit crazy trying to figure out why I always get the
> same unclear error: "01S02 Option Value Changed" when I do *any* bad
> action. Ie:
> 
> "SELECT * FROM tableThatDoesNotExist"
> "SELECT e FROM phptest" (when the "e" field doesn't exist)
> 
> instead of the native code/mesage. Note, that all works fine if there is
> no "human" error.


> I'm using php 4.1.1, unixODBC 2.0.8 as client and OOB - Access as
> server.
> 
> Thanks for any tip on how to solve this obscure problem.
> 
> Tomas V.V.Cox

01S02 is the ODBC defined State and the text for that state is
"option value changed". PHP does not give you the context of the
diagnostic because PHP ignores SQL_SUCCESS_WITH_INFO when attempting
to change the cursor to a dynamic cursor.

i.e.

the following code in PHPs php_odbc.c causes it:

        if (rc == SQL_SUCCESS) {
                if ((result->fetch_abs = (scrollopts &
SQL_FD_FETCH_ABSOLUTE))) 
{
                        /* Try to set CURSOR_TYPE to dynamic. Driver
will replace this with other
                           type if not possible.
                        */
                        if (SQLSetStmtOption(result->stmt,
SQL_CURSOR_TYPE, SQL_CURSOR_DYNAMIC)
                                == SQL_ERROR) {
                                odbc_sql_error(conn, result->stmt, "
SQLSetStmtOption");
                                SQLFreeStmt(result->stmt, SQL_DROP);
                                efree(result);
                                RETURN_FALSE;
                        }
                }
        } else {
                result->fetch_abs = 0;
        }

As PHP uses SQLError() to get diags and PHP is an ODBC 2.0 app the ODBC
spec says the diags stay in place until they are retrieved. So, what
happens is the above code is executed for each new statement and it
generates an informational diagnostic. Then, at some stage later
when you get an error, PHP pulls the first diag which is the one
above and not the one you want. In order to get the one you want you
will have to:

[1] Add a call to SQLError to the above code if SQLSetStmtOption
    returns SQL_SUCCESS_WITH_INFO - this will clear this diag of
    the ODBC driver (driver manager) stack.
[2] Change PHP to allow odbc_error etc to be called repeatedly
    until all diagnostics are cunsumed and you get the one you want.

Martin
--
Martin J. Evans
Easysoft Ltd, UK
Development