In the file ext/odbc/php_odbc.c

add an unsigned char called otype to the php function odbc_execute after populating *TMP, before calling convert_to_string save the value of (*TMP)->type into the otype buffer. Then at the end right before calling SQLPrepare (make sure it is the second call to SQLPrepare as the first is for pulling data from a file pointer and can't be null.) Check to see if otype == IS_NULL and if so set params[i-1].vallen = SQL_NULL_DATA. Problem solved. 

ex:

starting at line 919:

       for(i = 1; i <= result->numparams; i++) {
              if (zend_hash_get_current_data((*pv_param_arr)->value.ht, (void **) &tmp) == FAILURE) {
                php_error(E_WARNING,"Error getting parameter");
                SQLFreeStmt(result->stmt,SQL_RESET_PARAMS);
                efree(params);
                RETURN_FALSE;
            }
                  otype = (*tmp)->type;
              convert_to_string(*tmp);
                  if ((*tmp)->type != IS_STRING) {
                    php_error(E_WARNING,"Error converting parameter");
                    SQLFreeStmt(result->stmt, SQL_RESET_PARAMS);
                    efree(params);
                    RETURN_FALSE;
                }

              SQLDescribeParam(result->stmt, (UWORD)i, &sqltype, &precision,
                               &scale, &nullable);
                  params[i-1].vallen = (*tmp)->value.str.len;
              params[i-1].fp = -1;

                  if (IS_SQL_BINARY(sqltype))
                    ctype = SQL_C_BINARY;
              else
                ctype = SQL_C_CHAR;

                  if ((*tmp)->value.str.val[0] == '\'' &&
                      (*tmp)->value.str.val[(*tmp)->value.str.len - 1] == '\'') {
                    filename = &(*tmp)->value.str.val[1];
                    filename[(*tmp)->value.str.len - 2] = '\0';

                    if ((params[i-1].fp = open(filename,O_RDONLY)) == -1) {
                          php_error(E_WARNING,"Can't open file %s", filename);
                      SQLFreeStmt(result->stmt, SQL_RESET_PARAMS);
                          for(i = 0; i < result->numparams; i++) {
                            if (params[i].fp != -1) {
                                  close(params[i].fp);
                          }
                        }
                      efree(params);
                          RETURN_FALSE;
                  }

                    params[i-1].vallen = SQL_LEN_DATA_AT_EXEC(0);

                    rc = SQLBindParameter(result->stmt, (UWORD)i, SQL_PARAM_INPUT,
                                      ctype, sqltype, precision, scale,
                                            (void *)params[i-1].fp, 0,
                                          &params[i-1].vallen);
                } else {
#ifdef HAVE_DBMAKER
                  precision = params[i-1].vallen;
#endif
                  if(otype == IS_NULL)
                    {
                        params[i-1].vallen = SQL_NULL_DATA;
                }
                  rc = SQLBindParameter(result->stmt, (UWORD)i, SQL_PARAM_INPUT,
                                            ctype, sqltype, precision, scale,
                                          (*tmp)->value.str.val, 0,
                                        &params[i-1].vallen);
              }
              zend_hash_move_forward((*pv_param_arr)->value.ht);
           }