php - CodeIgniter modifications extending database drivers for using them with UNION queries -

my goal use union queries in codeigniter active record.

some people suggested me use method $this->db->last_query(); queries want, combining union.

problem $this->db->from(); method used in mysql driver in active record uses parenthesis around clause (ex: select * ('table') ) , prevents me use union.

so checked again , found modify _from_tables function defined in the

system/database/drivers/mysql/mysql_driver.php 

i changed code :

function _from_tables($tables) {     if ( ! is_array($tables))     {         $tables = array($tables);     } return '('.implode(', ', $tables).')'; } 

to :

function _from_tables($tables) {     if ( ! is_array($tables))     {         $tables = array($tables);     } return implode(', ', $tables); } 

but if asked question here on how extend ci mysql driver (in fact, want replace method custom one) : codeigniter hooks active record library , proposed ask new question.

so 1 user proposed add 2 files, did, in folders:

application/libraries/my_db_mysql_driver.php application/core/my_loader.php 

i these errors while using method :

 php error encountered severity: 8192 message: assigning return value of new reference deprecated filename: core/my_loader.php line number: 32 

so modified script gave me (you can see @ https://github.com/ellislab/codeigniter/wiki/extending-database-drivers) deleting & in :

$db =& new $my_driver(get_object_vars($db));  

i following error :

fatal error: call undefined method my_db_mysql_driver::where() in \system\libraries\session.php 

if has done without tweaking system folder, please :(