配列じゃない方のMap

Map.php

<?php
class Map{
	private $keys = [];
	private $values = [];
	
	function set($k, $v){
		$index = $this->getIndex($k);
		if($index === false){
			$this->keys[] = $k;
			$this->values[] = $v;
		}else{
			$this->keys[$index] = $k;
			$this->values[$index] = $v;
		}
	}
	function get($k){
		$index = $this->getIndex($k);
		return $index === false ? null : $this->values[$index];
	}
	function remove($k){
		$index = $this->getIndex($k);
		if($index === false){
			return false;
		}
		unset($this->keys[$index], $this->values[$index]);
		$this->keys = array_values($this->keys);
		$this->values = array_values($this->values);
		return true;
	}
	function clear(){
		$this->keys = [];
		$this->values = [];
	}
	private function getIndex($k){
		return array_search($k, $this->keys, true);
	}
}