Saving multiple checkbox into one column

I tried different ways to save multiple checkbox into database. I am so close right now but just last checkbox value are saving into database. I want them all and i couldn't make it. Here is my html codes.

<div class="col-xl-12">                     
<label>1st</label>
<input type="checkbox" name="data[]" value="00101"/>
<label>2nd</label>
<input type="checkbox" name="data[]" value="00102"/>
<label>3rd</label>
<input type="checkbox" name="data[]" value="00103"/>
<label>4th</label>
<input type="checkbox" name="data[]" value="00104"/>
</div>

In my controller.

  public function store(Request $request)
{

    $this->validate($request, array(
        'staff' => 'nullable',
        'dmc' => 'nullable',
        'workdone' => 'nullable',
        'product_id' => 'nullable'
    ));

    $ltjob = new Ltjob;
    $ltjob->staff = $request->staff;
    $ltjob->dmc = $request->dmc;
    $ltjob->product_id = $request->product_id;
    foreach ($request->input("data") as $data){
    $ltjob->workdone= $data;
}
    $ltjob->save();
    return redirect()->route('ltjobs.create');
}

Still saving last checkbox. When i try the dd($request->input("data")); before the foreach it gives me this:

  array:3 [▼
  0 => "00101"
  1 => "00102"
  2 => "00104"
]

And saving 00104. I hope you guys find the solution. And so sorry for my bad english. Thanks in advance.