I have a multiple file input field: <input type="file" id="documents" name="documents[]" multiple>

In my ProjectRequest class, I have the following rules applied:

$documents = count($this->input('documents'));
foreach(range(0, $documents) as $index) {
    $rules['documents.' . $index] = 'mimes:doc,pdf,jpeg,bmp,png|max:20000';
}

But when I try to upload a png or pdf I get the following validation error:

The documents.0 must be a file of type: doc, pdf, jpeg, bmp, png.

Update:

As suggested in the answers, instead of looping through the array, I directly added the documents.* rule in the $rules array. However I still get the same error.

In ProjecRequest:

$rules = [
  'documents.*' => 'mimes:doc,pdf,jpeg,bmp,png|max:20000',
];
return $rules;

In ProjectController@store:

public function store(ProjectRequest $request)
{
   $project = Project::create([
     /*key=>value removed to keep the question clean*/
   ]);

   foreach ($request->documents as $document) {
       $filename = $document->store('documents');
       Document::create([
          'project_id' => $project->id,
          'filepath' => $filename
       ]);
   }
   return redirect()->back();
}