How to fix 'Method [save] does not exist' error in PHP Laravel

I'm trying to save content of a dynamic form consist of dynamic drop down. I have use Ajax and java script to implement dynamic dropdown and use the get() function that part for data retrieval from the Database.

I have tried using first() instead of get(). But it leads to another error 'Trying to get property of non-object'. Also it results in disabling dynamic drop down option.

JobsController.php

function fetch(Request $request)
{
 $select = $request->get('select');
 $value = $request->get('value');
 $dependent = $request->get('dependent');
 $data = DB::table('specializations')->where($select, $value)**->first();**
 $output = '<option value="">--Select Specialization--</option>';
 foreach($data as $row)
 {
  $output .= '<option value="'.$row->id.'">'.$row->title.'</option>';
 }
 echo $output;

public function store(Request $request)
{
    $this->validate($request,[
        'expertise'=>'required',
        'specialization'=>'required'
    ]);

    $job = new JobsController;
    $job->expertise_id = $request->input('expertise');
    $job->specialization_id = $request->input('specialization');
    $job->save();

    return redirect('job.create_job')->with('success','Job Added');
}

create_job.blade.php

    {!! Form::open(['action'=>'JobsController@store','method'=>'POST'])!!}
        <div class="form-group">
            <label for="">Expertise</label>
            <select name="expertise" id="expertise" class="form-control input dynamic" data-dependent="specialization">
                    <option value="" disabled="true" selected="true">--Select your tradesmen--</option>
                    @foreach ($expertises as $expertise)
                    <option value=""></option>
                    @endforeach
            </select>
        </div>

        <div class="form-group">
            <label for="">Specialization</label>
            <select name="specialization" id="specialization" class="form-control input">
                <option value="">--Select Specialization--</option>
            </select>
        </div>

        
        

        {!! Form::close()!!}

I should be able to save the data. But save() method does not work and gives the error 'Method [save] does not exist' error.

via Chebli Mohamed