(PHP 4 = 4.0.6)
dbx_error() returns a string
containing the error message from the last function call of
the abstracted module (e.g. mysql module). If there are
multiple connections in the same module, just the last error
is given. If there are connections on different modules, the
latest error is returned for the module specified by the link_identifier parameter.
注: Always refer to the module-specific documentation as well.
The error message for Microsoft SQL Server is actually the result of the mssql_get_last_message() function.
The error message for Oracle (oci8) is not implemented (yet).