How to update image in laravel 5.6 - php

Question

I want to update an image in laravel 5.6.
In my app, the image is uploading and inserting into the database correctly but when I want to update the image it cannot update the old image.
How can I update the image with other field?
This is my view:
<form method="post" action="{{ route('employee.update', $employee->id) }}" enctype="multipart/form-data">
#csrf
#method("PATCH")
<input type="hidden" name="profile_old_image" value="{{$employee->profile_pic}}">
<div>
<input type="file" name="profile_pic" class="form-contrle" >
</div>
<div>
<input placeholder='Your Name' type='text' name='name' value="{{$employee->name}}" class="form-control">
</div>
</form>
This is my controller:
public function update(Request $request, $id)
{
$rules = [
'name' => 'required',
'father_name' => 'required',
'phone_no' => 'required',
'cnic' => 'required'
];
$validate = $this->validate($request, $rules);
$file = $request->file('profile_pic');
if($file == '')
{
$profile_pic = $request->profile_old_image;
}
else
{
$file = $request->file('profile_pic');
$fileName = time().'.'.$file->getClientOriginalExtension();
$destinationPath = public_path('/admin/images/employees');
$file->move($destinationPath,$fileName);
$profile_pic = '/admin/images/employees/'.$fileName;
}
//dd($request->all());
$employee = Employee::find($id);
$employee->name = $request->name;
$employee->father_name = $request->father_name;
$employee->phone_no = $request->phone_no;
$employee->cnic = $request->cnic;
$employee->desg_id = $request->desg_id;
$employee->profile_pic = $profile_pic;
$employee->save();
return redirect('admin/employee')->with('message', 'Records Successfully Updated');
}