PHP error connecting to MS SQL 2005 using CodeIgniter - php

Question

I'm encountering an error every time I'm connecting to my MS SQL 2005 database using CodeIgniter framework, I'm using PHP 5.6.8 version.`
"Fatal error: Call to undefined function sqlsrv_connect() in C:\xampp\htdocs\my_website\system\database\drivers\sqlsrv\sqlsrv_driver.php
on line 76"
I've already added dll files php_pdo_sqlsrv_56_ts.dll and php_sqlsrv_56_ts.dll to ext folder and on my php.ini, and installed Microsoft SQL Native Client 2012,
this is my code in the sqlsrv_driver.php line 76 -> return sqlsrv_connect($this->hostname, $connection);
I already setup and installed all needed files but still I encounter this error, and NO sqlsrv in phpinfo(), so I created a sample php file to test if I will connect to my database w/out using a framework and its successfully connected in MS SQL database, However it doesn't if I used codeigniter.
Did I miss some code, configuration or software to install? Thanks for usual support!
This is my database.php
$db['default']['hostname'] = 'MY-PC\MSSQL2005';
$db['default']['username'] = 'sa';
$db['default']['password'] = 'password';
$db['default']['database'] = 'MYDB';
$db['default']['dbdriver'] = 'sqlsrv';
$db['default']['dbprefix'] = '';
$db['default']['pconnect'] = FALSE;
$db['default']['db_debug'] = TRUE;
$db['default']['cache_on'] = FALSE;
$db['default']['cachedir'] = '';
$db['default']['char_set'] = 'utf8';
$db['default']['dbcollat'] = 'utf8_general_ci';
$db['default']['swap_pre'] = '';
$db['default']['autoinit'] = TRUE;
$db['default']['stricton'] = FALSE;