Deduces the season based on a given date

seasoning.php

<?php

function get_season($hemisphere = 'northern', $date = '') {
  $now = (!empty($date)) ? strtotime($date) : strtotime(date('Y/m/d'));
  $season_dates = array(
    'northern' => array(
      '/03/21' => 'spring',
      '/06/21' => 'summer',
      '/09/21' => 'autumn',
      '/12/21' => 'winter',
    ),
    'soutern' => array(
      '/03/21' => 'autumn',
      '/06/21' => 'winter',
      '/09/21' => 'spring',
      '/12/21' => 'summer',
    ),
  );

  $previous = strtotime(date('Y') . '01/01');
  $previous_season = $result = 'winter';
  foreach ($season_dates[$hemisphere] as $key => $value) {
    $start = $previous;
    $end = strtotime(date('Y') . $key);

    if ($now >= $start && $now < $end) {
      $date = date('Y') . $key;
      $result = $previous_season;
    }
    $previous_season = $value;
    $previous = $end;
  }

  return $result;
}