PHP Count the number of working days between two dates.

gistfile1.php

<?php

/**
 * Count the number of working days between two dates.
 *
 * This function calculate the number of working days between two given dates,
 * taking account of the Public festivities, Easter and Easter Morning days,
 * the day of the Patron Saint (if any) and the working Saturday.
 *
 * @param   string  $date1    Start date ('YYYY-MM-DD' format)
 * @param   string  $date2    Ending date ('YYYY-MM-DD' format)
 * @param   boolean $workSat  TRUE if Saturday is a working day
 * @param   string  $patron   Day of the Patron Saint ('MM-DD' format)
 * @return  integer           Number of working days ('zero' on error)
 *
 * @author Massimo Simonini <[email protected]>
 */
function getWorkdays($date1, $date2, $workSat = FALSE, $patron = NULL) {
  if (!defined('SATURDAY')) define('SATURDAY', 6);
  if (!defined('SUNDAY')) define('SUNDAY', 0);

  // Array of all public festivities
  $publicHolidays = array('01-01', '01-06', '04-25', '05-01', '06-02', '08-15', '11-01', '12-08', '12-25', '12-26');
  // The Patron day (if any) is added to public festivities
  if ($patron) {
    $publicHolidays[] = $patron;
  }

  /*
   * Array of all Easter Mondays in the given interval
   */
  $yearStart = date('Y', strtotime($date1));
  $yearEnd   = date('Y', strtotime($date2));

  for ($i = $yearStart; $i <= $yearEnd; $i++) {
    $easter = date('Y-m-d', easter_date($i));
    list($y, $m, $g) = explode("-", $easter);
    $monday = mktime(0,0,0, date($m), date($g)+1, date($y));
    $easterMondays[] = $monday;
  }

  $start = strtotime($date1);
  $end   = strtotime($date2);
  $workdays = 0;
  for ($i = $start; $i <= $end; $i = strtotime("+1 day", $i)) {
    $day = date("w", $i);  // 0=sun, 1=mon, ..., 6=sat
    $mmgg = date('m-d', $i);
    if ($day != SUNDAY &&
      !in_array($mmgg, $publicHolidays) &&
      !in_array($i, $easterMondays) &&
      !($day == SATURDAY && $workSat == FALSE)) {
        $workdays++;
    }
  }

  return intval($workdays);
}

Great work! This inspired me to create a PHP object that implements some of your ideas.
WorkingDayHelper class

=== UPDATE ===

The Gist is abandoned in favor of a complete Github repo that contains the library, a better README, and the Composer installer.
Give a try to letsjump/workday-helper-php

It counts the workdays and also returns a calendar of closing events for the specified range of dates.

@letsjump, great job!

Correect me if I'm wrong, but this appears to count Good Friday (day before Easter weekend) as a working day. Is that the case?

Correect me if I'm wrong, but this appears to count Good Friday (day before Easter weekend) as a working day. Is that the case?

Yes, Good Friday is a working day (almost anywhere), but I think it can be excluded from counting if you specify the date in the $publicHolidays array.

Anyway, this is an old job, please take a look at the @letsjump package!