Sort various (clothing) sizes in an array

ObjectSize.php

<?php

class ObjectSize {

  protected static $sizes = [
    'xxxxl',
    'xxxl',
    'xxl',
    'xl',
    'l',
    'm',
    's',
    'xs',
    'xxs',
    'xxxs'
  ];

  public static function classify($value=null)
  {

    $value = mb_strtolower(trim($value));

    // handle ranges
    if (mb_strpos($value, '-')) {
      $values = explode('-', $value);
      $part1 = self::classify($values[0]);
      if ($part1) {
        $part2 = self::classify($values[1]);
        return $part1 - ($part2 / 100);
      }
      return false;
    }

    // handle clothing sizes
    if ($clothingSizeIndex = array_search($value, ObjectSize::$sizes)) {
      return $clothingSizeIndex * -1;
    }

    return false;
  }

  public static function compare($a, $b)
  {
    $classA = self::classify($a);
    $classB = self::classify($b);

    if ($classA && $classB) {
      if ($classA == $classB) return 0;
      return $classA > $classB ? 1 : -1;
    }

    return strnatcmp($a, $b);
  }

  public static function sort(array $arr)
  {
    usort($arr, 'self::compare');
    return $arr;
  }
}

usage.php

<?php
  require 'ObjectSize.php';
  $sizes = [
    'XL',
    1,
    5,
    6,
    'L',
    4.5,
    '3.33',
    '3,25',
    'XXL',
    'L-XXL',
    'L-XXXL',
    'a',
    'ba',
    'aaaa',
    'S',
    '5-50',
    '5/6',
    '50x80cm',
    'L-XL',
    'M',
    10,
    '104-15',
    'A/75',
    1,
    'A/70',
    'ab',
    'XS',
    'XXS'
  ];
?>

<h1>Original sizes</h1>
<pre><?= print_r($sizes); ?></pre>

<h1>Classified sizes</h1>
<pre><?= print_r(array_map('ObjectSize::classify', $sizes));  ?></pre>

<h1>Sorted sizes</h1>
<pre><?= print_r(ObjectSize::sort($sizes)); ?></pre>