Get working days between two dates, with custom off day

/**
 * Get working days between two dates, with custom off day
 *
 * @param Date $startDate End Date
 * @param Date $endDate To date
 * @param Array $holidays Week Number in Single dimension array
 * @return integer
 */
 
function getWorkingDays_customOffDay($startDate, $endDate, $holidays) {
 
    $day = 86400; // Day in seconds
 
    $sTime = strtotime($startDate); // Start as time
    $eTime = strtotime($endDate); // End as time
    $numDays = round(($eTime - $sTime) / $day) + 1;
 
    $days = array();
 
    for ($d = 0; $d < $numDays; $d++) {
        $day_number = date('N', ($sTime + ($d * $day)));
        if (!in_array($day_number, $holidays)) {
            $days[] = date('Y-m-d N', ($sTime + ($d * $day)));
        }
    }
 
    return count($days);
 
}