Last date of this month in php

{ // deep_execution_view
const authorName = "Ankit Agrawal";
//
const publishDate = "January 12, 2016";

$last_date_this_month =strtotime('last day of this month') ;

echo 'Last date of this month: '.$last = date('d/m/Y', $last_date_this_month);

}