config.php - configuration file
load.php - It will load all the necessary backend code
check.php - Checking for user cookie
db.class.php - Miscellaneous functions
filter.class.php - Filter the input and prevent from unwanted hacks.
Note: return 1(success) or -1(fails).
* Filter::check_string($str)
* Filter::check_number($num)
* Filter::check_num_text($val)
* Filter::check_dob($dob) `01/09/2023`
* Filter::check_gst($number)
* Filter::check_status($val) `expected $val - 0,1,2,-1`
* Filter::is_email($mail)
* Filter::check($ip)
* Filter::link($link)
Note: return $data.
* Filter::input(val) `it return the filtered data
session.class.php - set,get,delete,destory the session
* Session::set($key,$value)
* Session::get($key)
* Session::isset($key)
* Session::destroy()
* Session::delete($key)
* Session::unset()
```