title: how to edit pdf file in laravel 5.6. Save same file if not edited or another selected file?
body: <p>I want to update the file in laravel 5.6. But the file is not showing in edit.blade.php. When i click update button the file goes null..</p>
  
  <p>editfile.blade.php</p>
  
  <pre><code>&lt;div class="control-group"&gt;
            &lt;label class="control-label"&gt;Publication File&lt;/label&gt;
            &lt;div class="controls"&gt;
              &lt;input type="file" name="publication_file" id="publication_file" value=" {{ $publicationDetails-&gt;publication_file }}"&gt; &lt;span&gt; {{ $publicationDetails-&gt;publication_file }} &lt;/span&gt;
            &lt;/div&gt;
          &lt;/div&gt; 
  </code></pre>
  
  <p>Update function in controller</p>
  
  <pre><code> if($request-&gt;isMethod('post')){
          $data = $request-&gt;all();
  
          Publication::where(['publication_id'=&gt;$publication_id])-&gt;update(['publication_title' =&gt; $data['publication_title'],'publication_type'=&gt;$data['publication_type'],'publication_file'=&gt;$data['publication_file']]);
         return redirect('/admin/view-publication')-&gt;with('flash_message_success','Publication Updated Successfully..');
      }
      $publicationDetails = Publication::where(['publication_id'=&gt;$publication_id])-&gt;first();
      return view('admin.publication.edit_publication')-&gt;with(compact('publicationDetails'));
  </code></pre>