Start and end days of week based on the first day of the week

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// PHP Code for Determining Start and End Days of the Week Based on a Specified First Day
 
// Define the starting day of the week (0 for Sunday, 1 for Monday)
$week_start_day = 0;
 
// Create DateTime objects for the current date and time
$date_time_from = new DateTime('now');
$date_time_to = clone $date_time_from;
 
// Calculate the first day of the current week
$this_week_first_day =
  $date_time_from->setISODate(
    $date_time_from->format('Y'),
    $date_time_from->format('W'),
    $week_start_day
  );
 
// Calculate the last day of the current week
$this_week_last_day =
  $date_time_to->setISODate(
    $date_time_to->format('Y'),
    $date_time_to->format('W'),
    (6 + $week_start_day)
  );
 
// Set the time to the start of the day and end of the day, respectively
$this_week_first_day->modify('00:00:00.000000');
$this_week_last_day->modify('23:59:59.999999');
 
// Now, $this_week_first_day and $this_week_last_day represent the start and end of the current week.
Programming Language: PHP