class SortArray

class SortArray {
    
    /**
     * Sorts a structured array by the 'weight' element.
     *
     * Note that the sorting is by the 'weight' array element, not by the render
     * element property '#weight'.
     *
     * Callback for uasort().
     *
     * @param array $a
     *   First item for comparison. The compared items should be associative
     *   arrays that optionally include a 'weight' element. For items without a
     *   'weight' element, a default value of 0 will be used.
     * @param array $b
     *   Second item for comparison.
     *
     * @return int
     *   The comparison result for uasort().
     */
    public static function sortByWeightElement(array $a, array $b) {
        return static::sortByKeyInt($a, $b, 'weight');
    }
    
    /**
     * Sorts a structured array by '#weight' property.
     *
     * Callback for uasort().
     *
     * @param array $a
     *   First item for comparison. The compared items should be associative
     *   arrays that optionally include a '#weight' key.
     * @param array $b
     *   Second item for comparison.
     *
     * @return int
     *   The comparison result for uasort().
     */
    public static function sortByWeightProperty($a, $b) {
        return static::sortByKeyInt($a, $b, '#weight');
    }
    
    /**
     * Sorts a structured array by 'title' key (no # prefix).
     *
     * Callback for uasort().
     *
     * @param array $a
     *   First item for comparison. The compared items should be associative arrays
     *   that optionally include a 'title' key.
     * @param array $b
     *   Second item for comparison.
     *
     * @return int
     *   The comparison result for uasort().
     */
    public static function sortByTitleElement($a, $b) {
        return static::sortByKeyString($a, $b, 'title');
    }
    
    /**
     * Sorts a structured array by '#title' property.
     *
     * Callback for uasort().
     *
     * @param array $a
     *   First item for comparison. The compared items should be associative arrays
     *   that optionally include a '#title' key.
     * @param array $b
     *   Second item for comparison.
     *
     * @return int
     *   The comparison result for uasort().
     */
    public static function sortByTitleProperty($a, $b) {
        return static::sortByKeyString($a, $b, '#title');
    }
    
    /**
     * Sorts a string array item by an arbitrary key.
     *
     * @param array $a
     *   First item for comparison.
     * @param array $b
     *   Second item for comparison.
     * @param string $key
     *   The key to use in the comparison.
     *
     * @return int
     *   The comparison result for uasort().
     */
    public static function sortByKeyString($a, $b, $key) {
        $a_title = is_array($a) && isset($a[$key]) ? $a[$key] : '';
        $b_title = is_array($b) && isset($b[$key]) ? $b[$key] : '';
        return strnatcasecmp($a_title, $b_title);
    }
    
    /**
     * Sorts an integer array item by an arbitrary key.
     *
     * @param array $a
     *   First item for comparison.
     * @param array $b
     *   Second item for comparison.
     * @param string $key
     *   The key to use in the comparison.
     *
     * @return int
     *   The comparison result for uasort().
     */
    public static function sortByKeyInt($a, $b, $key) {
        $a_weight = is_array($a) && isset($a[$key]) ? $a[$key] : 0;
        $b_weight = is_array($b) && isset($b[$key]) ? $b[$key] : 0;
        if ($a_weight == $b_weight) {
            return 0;
        }
        return $a_weight < $b_weight ? -1 : 1;
    }

}