methodNotAllowed(array('GET', 'HEAD')) in RouteCollection.php laravel 5.0 - laravel

Question

I want to login as I submit the form but I am getting an error.
The form code is as follows:
{!! Form::open() !!}
{{ $errors->first("parentPassword") }}<br />
<div>
<legend>Parent</legend>
Email<br>
<input type="email" id="email" name="parentEmail" required>
<br>
Password<br>
<input type="password" name="parentPassword">
<br><br>
</div>
{!!Form::submit('Submit',array('class' => 'btn btn-outline btn-primary')) !!} </fieldset>
{!! Form::close() !!}
The controller code is as follows:
App\Http\Controllers;
use Illuminate\Support\Facades\Redirect;
class loka extends Controller
{
public function login()
{
if ($this->isPostRequest()) {
$validator = $this->getLoginValidator();
if ($validator->passes()) {
$credentials = $this->getLoginCredentials();
if (Auth::attempt($credentials)) {
return redirect()->intended('/');
}
return Redirect::back()->withErrors([
"parentPassword" => ["Credentials invalid."]
]);
} else {
return Redirect::back()
->withInput()
->withErrors($validator);
}
}
return view("signup.index");
}
protected function isPostRequest()
{
// return Request::isMethod('post');
}
protected function getLoginValidator()
{
return Validator::make(Request::all(), [
"parentEmail" => "required",
"parentPassword" => "required"
]);
}
protected function getLoginCredentials()
{
return [
"parentEmail" => Request::input("parentEmail"),
"parentPassword" => Request::input("parentPassword")
];
}
}
The route is as follows:
Route::patch("/index", [
"as" => "login/index",
"uses" => "loka#login"
]);