How to get column is Null and condition in php laravel

You can use sub query to achieve this i haven't tested it but you can give it a try.

Hak::where('UserID', 23)->where('isUsed', 0)->where(function ($q){
   $q->whereNull('ExpDate')
   ->orWhere('ExpDate', '>', '2019-09-05');        
})->get();

i think i would write the SQL as followes as OR optimizes badly in MySQL..
Pretty sure fully supported Parallel Query Execution will change that in the future.
As they are working on this feature if you want you can read MySQL 8.0.14: A Road to Parallel Query Execution is Wide Open!

The SQL result might be wrong as you didn't provide example data and expected result see Why should I provide a Minimal Reproducible Example for a very simple SQL query? for providing those.

Query

SELECT 
 *
FROM 
 your_table
WHERE 
   UserID = 23
 AND
   isUsed = 0
 AND
  ExpDate >  '2019-09-05'


UNION ALL

SELECT 
 *
FROM 
 your_table
WHERE 
   UserID = 23
 AND
   isUsed = 0
 AND 
   ExpDate IS NULL

Laravel code

To warn you i didn't program in Laravel for some time now so this code might be wrong.

<?php
 $first = DB::table('your_table')
            ->select('your_table.*')
            ->where('UserID ', '=', 1)
            ->andWhere('isUsed ', '=', 0)
            ->andWhere('ExpDate ', '>', '2019-09-05')  
 ;

 $second = DB::table('your_table')
             ->select('your_table.*')
            ->where('UserID ', '=', 1)
            ->andWhere('isUsed', '=', 0)
            ->whereNull('ExpDate') 

            ->union($first)
            ->get();
?> 

It can be confusing coming from SQL, but you'll need two orWhere in Eloquent to achieve this. So basically:

Hak::orWhereNull('ExpDate')
        ->orWhere('ExpDate', '>', '2019-09-05')
        ->where('UserID', 23)
        ->get()

EDIT: Haven't tested it though, but you might need a subquery to filter the userId as well.