Laravel 5.4 where clauses if $request->jobTitle !null?

I built small search form helps me search in jobsTable from db

jobs Table has jobTitle, jobCompany, jobGovernorate, jobLocation and created_at column

And posted data from search form:

{"jobTitle":"designer","jobCompany":null,"jobGovernorate":null,"jobLocation":null,"postingDate":"ad"}

I mean some input may be null, so how to write dynamic where clause for inputs have value, i want search engine able to search by JobTitle, JobCompany or All inputs if have value.

Hint: fields name and table columns name are same

if there's a way to retrieve jobs from my db like

DB::table('jobs')->where($request->all())

Sorry for poor english, I don't know how to explain my question

via Uk63