<?php    $today = date("y-m-d");    $filter = ['2019-06-18'];    // Api Request    $a = ordersRequest("statistics/list", array("idapp" => 11111));    $links = $a['statistics']['grp_date'];    $filtered = array_filter($links, function ($item) use ($filter) {    return in_array($item['date'], $filter);    });    print_r($filtered);     ?>這個作品：$filter = ['2019-06-02'];但是我怎樣才能在這個變量中獲得當前日期？$filter = ['$today'];$filter = [$today];$filter = date("y-m-d");不適合我