php 双向队列

<?php 
class deque
{
	public $queue  = array();
	public $length = 0;
   
	public function frontAdd($node){
		array_unshift($this->queue,$node);
		$this->countqueue();
	}
	public function frontRemove(){
		$node = array_shift($this->queue);
		$this->countqueue();
		return $node;
	}
	  
	public function rearAdd($node){
		array_push($this->queue,$node);
		$this->countqueue();
	}
	 
	public function rearRemove(){
		$node = array_pop($this->queue);
		$this->countqueue();
		return $node;
	}
	 
	public function countqueue(){
		$this->length = count($this->queue);    
	}
}
$fruit = new deque();
echo $fruit -> length;
$fruit -> frontAdd("Apple");
$fruit -> rearAdd("Watermelon");
echo '<pre>';
print_r($fruit);
echo '</pre>';
?>