<?php
function quarter_day($time = "") {
$time = $time ? strtotime($time) : time();
$date = intval(date("j", $time));
$month = intval(date("n", $time));
$year = intval(date("Y", $time));
// get selected quarter as number between 1 and 4
$quarter = ceil($month / 3);
// get first month of current quarter as number between 1 and 12
$fmonth = $quarter + (($quarter - 1) * 2);
// map days in a year by month
$map = [31,28,31,30,31,30,31,31,30,31,30,31];
// check if year is leap
if (((($year % 4) == 0) && ((($year % 100) != 0) || (($year % 400) == 0)))) $map[1] = 29;
// get total number of days in selected quarter, by summing the relative portion of $map array
$total = array_sum(array_slice($map, ($fmonth - 1), 3));
// get number of days passed in selected quarter, by summing the relative portion of $map array
$map[$month-1] = $date;
$day = array_sum(array_slice($map, ($fmonth - 1), ($month - $fmonth + 1)));
return "Day $day on $total of quarter $quarter, $year.";
}
print(quarter_day("2017-01-01")) . "\n"; // prints Day 1 on 90 of quarter 1, 2017.
print(quarter_day("2017-04-01")) . "\n"; // prints Day 1 on 91 of quarter 2, 2017.
print(quarter_day("2017-08-15")) . "\n"; // prints Day 46 on 92 of quarter 3, 2017.
print(quarter_day("2017-12-31")) . "\n"; // prints Day 92 on 92 of quarter 4, 2017.