gistfile1.php[345]

<?php 

class Link {
	public $value;
	public $next;

	public function __construct($value) {
		$this->value = $value;
	}

	public function displayLink() {
		echo $this->value.' ';	
	}
	
}

class FirstLastList {
	public $first;
	public $last;
	
	public function __construct() {
		$this->first = null;
		$this->last = null;	
	}
	
	public function isEmpty() {
		return empty($this->first);
	}

	public function insertLast($value) {
		$link = new Link($value);
		
		if ($this->isEmpty()) {
			$this->first = $link;
		} else {
			$this->last->next = $link;
		}	
		
		$this->last = $link;
	}
	
	public function deleteFirst() {
		if ($this->isEmpty()) {
			return null;
		}
		
		$first = $this->first;

		if ($this->first->next == null) {

			$this->first = null;
			$this->last = null;

			return $first; 
		}

		$this->first = $this->first->next;

		return $first;
	}
	
	public function displayList() {
		$current = $this->first;

		while ($current != null) {
			$current->displayLink();
			$current = $current->next;
		}
	}
}


class LinkQueue {
	private $linkList = null;

	public function __construct() {
		$this->linkList = new FirstLastList();
	}

	public function insert($value) {
		$this->linkList->insertLast($value);
	}

	public function remove() {
		$this->linkList->deleteFirst();
	}

	public function display() {
		$this->linkList->displayList();
	}
}


$queue = new LinkQueue();
$queue->insert(10);
$queue->insert(20);
$queue->insert(30);
$queue->insert(40);
$queue->display();
echo "/n";

$queue->remove();
$queue->display();
echo "/n";
?>