Passing value from url to controller in Laravel

I have created an a tag in my x.blade.pdp file

<a href="" class= "text-center">Print Certificate</a>

In web.php

Route::get('/certificate/pdf/{$year}','PDFController@export_pdf');

My Controller

public function export_pdf( $year)

But when I click on the link the page cannot be displayed. I would like to use the $year in the where clause .

Please I need some assistance

via Chebli Mohamed