A very simple solution using Carbon\Caborn
here is the repository file which is called from a controller store function
<?php
namespace App\Repositories\Leave;
use App\Models\Holiday;
use App\Models\LeaveApplication;
use App\Repositories\BaseRepository;
use Carbon\Carbon;
class LeaveApplicationRepository extends BaseRepository
{
    protected $holiday;
    public function __construct(LeaveApplication $model, Holiday $holiday)
    {
        parent::__construct($model);
        $this->holiday = $holiday;
    }
    /**
     * Get all authenticated user leave
     */
    public function getUserLeave($id)
    {
        return $this->model->where('employee_id',$id)->with(['leave_type','approver'])->get();
    }
    /**
     * @param array $request
     */
    public function create($request)
    {
        $request['total_days'] = $this->getTotalDays($request['start_date'],$request['end_date']);
        return $this->model->create($request->only('send_to','leave_type_id','start_date','end_date','desc','total_days'));
    }
    /**
     * Get total leave days
     */
    private function getTotalDays($startDate, $endDate)
    {
        $holidays = $this->getHolidays(); //Get all public holidays
        $leaveDays = 0; //Declare values which hold leave days
        //Format the dates
        $startDate = Carbon::createFromFormat('Y-m-d',$startDate);
        $endEnd = Carbon::createFromFormat('Y-m-d',$endDate);
        //Check user dates
        for($date = $startDate; $date <= $endEnd; $date->modify('+1 day')) {
            if (!$date->isWeekend() && !in_array($date,$holidays)) {
                $leaveDays++; //Increment days if not weekend and public holidays
            }
        }
        return $leaveDays; //return total days
    }
    /**
     * Get Current Year Public Holidays
     */
    private function getHolidays()
    {
        $holidays = array();
        $dates = $this->holiday->select('date')->where('active',1)->get();
        foreach ($dates as $date) {
            $holidays[]=Carbon::createFromFormat('Y-m-d',$date->date);
        }
        return $holidays;
    }
}
Controller function receives user input request and validate before call the repository function
<?php
namespace App\Http\Controllers\Leave;
use App\Http\Controllers\AuthController;
use App\Http\Requests\Leave\LeaveApplicationRequest;
use App\Repositories\Leave\LeaveApplicationRepository;
use Exception;
class LeaveApplicationController extends AuthController
{
    protected $leaveApplication;
    /**
     * LeaveApplicationsController constructor.
     */
    public function __construct(LeaveApplicationRepository $leaveApplication)
    {
        parent::__construct();
        $this->leaveApplication = $leaveApplication;
    }
    /**
     * Store a newly created resource in storage.
     */
    public function store(LeaveApplicationRequest $request)
    {
        try {
            $this->leaveApplication->create($request);
            return $this->successRoute('leaveApplications.index','Leave Applied');
        }
        catch (Exception $e) {
            return $this->errorWithInput($request);
        }
    }
}