Slack message every last working day of the month

<?php

for ($i =1; $i < 12; $i++ ) {
    echo "/remind #channel to BLABLABLA on " . getFriday($i, 2019) . " 16:30 \n";
}

function getFriday($m,$y) {
$dateString = "$y-$m-01";

$newdate = date("Y-m-t", strtotime($dateString));
$lastworkingday = date('l', strtotime($newdate));

if($lastworkingday == "Saturday") { 
$newdate = date ( 'Y-m-j', strtotime ('-2 day', strtotime($newdate)));
}
elseif($lastworkingday == "Sunday") { 
$newdate = date ( 'Y-m-j', strtotime ('-2 day', strtotime($newdate)));
}

return date('Y-m-j', strtotime($newdate));

}