Adding item to array or change existent item position after shifting elements up or down depending on available positions

ArrayManipulation.php

<?php
/**
 * Author:Wajdi Jurry <[email protected]> (https://github.com/wajdijurry)
 * Gist: https://gist.github.com/wajdijurry/a00752123134342ccc9d13a480c9f013
 */

class ArrayManipulation
{
    private $array;
    public function __construct(array $array)
    {
        $this->array = $array;
    }
    /**
     * Add/Change item position in array
     * Shifting elements up/down depending on available positions
     * Priority for shifting down
     * @param int $position
     * @param string $itemId
     * @return array
     */
    public function addItemChangePosition(int $position, string $itemId)
    {
        $max = 5; // Max number of elements in array
     
        if ($position >= $max || $position < 0) {
          exit('Wrong Position');
        }
        
        // Remove item if exists
        if (($key = array_search($itemId, $this->array)) !== false) {
            unset($this->array[$key]);
        }

        $newArr = [];
        if (array_key_exists($position, $this->array)) {
          
            /**
             * Determing shifting up or down
             * Shifting up: 1, Shifting Down: -1
             */
            $operator = (array_sum(array_keys($this->array)) >= array_sum(range($position, $max-1))) ? 1 : -1;
            
            //Iterate over array, starting from $position till nonexistent element
            for ($i = $position; $i >= $position *  (-$operator); $i = $i - $operator) {
                if (!array_key_exists($i, $this->array)) {
                    // Exit loop if element does not exist
                    break;
                }
              
                // Add items-to be shifted to $newArr
                $newArr[$i - $operator] = $this->array[$i];
              
                // Remove from original array (avoiding duplicate)
                unset($this->array[$i]);
            }
          
            // Merging shifted elements with non-affected elements, keys preserved
            $this->array = $newArr + array_diff($this->array, $newArr);
        }
      
        // Add new item to array
        $this->array[$position] = $itemId;
        
        // Sort array
        ksort($this->array, SORT_NUMERIC);

        return $this->array;
    }
}

// Example 1:
$items = [
  0 => 'item1',
  1 => 'item2'
];
print_r($items = (new ArrayManipulation($items))->addItemChangePosition(1, 'new item'));  // $items = [0 => 'item1', 1 => 'new item', 2 => 'item2']
        
// Example 2:
$items = [
  0 => 'item1',
  3 => 'item2'
];
print_r($items = (new ArrayManipulation($items))->addItemChangePosition(3, 'new item'));  // $items = [0 => 'item1', 3 => 'new item', 4 => 'item2']
        
// Example 3:
$items = [
  1 => 'item1',
  2 => 'item2',
  3 => 'item3',
  4 => 'item4'
];
print_r($items = (new ArrayManipulation($items))->addItemChangePosition(4, 'new item'));  // $items = [0 => 'item1', 1 => 'item2', 2 => 'item3', 3 => 'item4', 4 => 'new item']

// Example 3:
$items = [
  1 => 'item1',
  2 => 'item2',
  3 => 'item3',
  4 => 'item4'
];
print_r($items = (new ArrayManipulation($items, ))->addItemChangePosition(2, 'item4'));  // $items = [1 => 'item1', 2 => 'item4', 3 => 'item2', 4 => 'item3']