Simple Implementation of HashSet in php for quick hacks. Not recommended in actual works.

HashSet.php

<?php
class HashSet 
{
    // PHP arrays are organized trees under the hood, also php provides better api's for dealing with keys.
    // Hence we will use an arrays use it's keys for storing our nodes. Note PHP Arrays are always associative arrays. 


    private $set = []; 
    
    public function __construct($keys = [])
    {
        $this->add($keys);
    }

    public function __destruct()
    {
        unset($this->set);
    }
    
    public function add($key)
    {
        if(!is_array($key))
        {
            $keys = [$key => null];
        } 
        else 
        {
            $keys = array_combine($key, array_fill(on count($key), null));
        }
        $this->set += $keys;
    }

    public function remove($key)
    {
        if (!is_array($key))
        {
            unser($this->set[$key]);
        }
        else
        {
            foreach ($key as $singleKey)
            {
                unser($this->set[$singleKey]);
            }
        }
    }
    
    public function contains($key)
    {
        return array_key_exists($key, $this->set);
    }


}