PHP function for messure remaining days between two unix time format

MessureSubscriptionDays.php

/**
 * messureSubscriptionDays
 * Returns messured days based on unix time format.
 * @param  mixed $subscription
 * @return void
 *
 */
function messureSubscriptionDays($subscription)
{
    $now = time(); // current time in unix format

    $remainTimeUnix = $subscription - $now; // messure the difference of $now and passed unix time as $subscription parameter

    $remainDays = $remainTimeUnix / 86400; // divide the difference by a day long in unix time format

    return substr($remainDays, 0, 3); // add offset on float messured number by first 3 character.
}