<?php

function endOfSubscriptionIsNear1(
    DateTime $today,
    DateTime $endOfSubscription
) {
    return $endOfSubscription < $today->modify('+15 days');
}

function endOfSubscriptionIsNear2(
    DateTime $endOfSubscription
) {
    return $endOfSubscription < (new DateTime)->modify('+15 days');
}

$closedEndOfSubscription = (new DateTime)->modify('+14 days');
$farEndOfSubscription = (new DateTime)->modify('+16 days');

vprintf("Using new object should be 1: %d\n", endOfSubscriptionIsNear1(new DateTime, $closedEndOfSubscription));
vprintf("Using new object should be 0: %d\n", endOfSubscriptionIsNear1(new DateTime, $farEndOfSubscription));

$today = new DateTime;
$endOfSubscription = (new DateTime)->modify('+16 days');

vprintf("First call: %d\n", endOfSubscriptionIsNear1($today, $endOfSubscription));
vprintf("Second call: %d\n", endOfSubscriptionIsNear1($today, $endOfSubscription));