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EXAMPLE 1:
      
      // example of creating an enum in PHP
      <?php

        abstract class PeriodEnum {
          const Day = 'day';
          const Week = 'week';
          const Month = 'month';
          const All = 'all';

          public static function isValidPeriod($period, $strict = false) {
            $constants = array(self::Day => self::Day, self::Week => self::Week, self::Month => self::Month, self::All => self::All);

            if ($strict) {
              return array_key_exists($period, $constants);
            }

            $keys = array_map('strtolower', array_keys($constants));

            return in_array(strtolower($period), $keys);
          }
        }

      ?>
      
    
EXAMPLE 2:
      
      // example of creating a clamp function in PHP
      <?php

        function clamp($current, $min, $max) {
            return max($min, min($max, $current));
        }

      ?>